Way OT-car mileage with mid grade fuel

[oldpotatoe]

2017 VW 'S', 4 Motion. 85 octane-26-27 mpg, mixed use. 87 octane(recommended), 29-30 mpg, same use. Is the increased mileage the octane or me driving different or???. You car guys, what sayeth y'all?

[GScot]

2017 VW 'S', 4 Motion. 85 octane-26-27 mpg, mixed use. 87 octane(recommended), 29-30 mpg, same use. Is the increased mileage the octane or me driving different or???. You car guys, what sayeth y'all?

Turbo engine and the management of fuel is very precise. It's plausible that the mileage is better with higher octane fuel as the computer can allow more boost. Try some premium and see if it gets even better, but I bet mid-grade is probably the limit of improvement. However, your high altitude may allow it to do more that it would for us down the mountain.

[David Kirk]

Pretty hard to be sure. If the car can advance the timing to take advantage of the higher octane then it could make more power for sure and one would assume there would be a gain in efficiency. I'd run a few tanks of the low and a few tanks of the high so that you have a larger sample size and that might give a better idea of what's up.

dave

[ftf]

2017 VW 'S', 4 Motion. 85 octane-26-27 mpg, mixed use. 87 octane(recommended), 29-30 mpg, same use. Is the increased mileage the octane or me driving different or???. You car guys, what sayeth y'all?

If it is designed for 87, it will retard the timing if you use 85, this means the engine will be less efficient, less power etc.

[ojingoh]

If it is designed for 87, it will retard the timing if you use 85, this means the engine will be less efficient, less power etc.

This. The car's brain will retard the spark and/or squirt more fuel into the cylinder to prevent knocking - aka early detonation due to pressure and heat. End result is a loss of power.

[Mikej]

My guess is first tank of summer gas blend ? As far as the timing and spark with more octane, more likely you could gain power but not mpg.

[choke]

I think you definitely need to run more than one tank to get a feel for what it does. I recently had a tank that was 2mpg more than normal and I drove like I typically do. I also purchased it from the station that I usually go to...so there's no apparent reason for the difference.

If it is designed for 87, it will retard the timing if you use 85, this means the engine will be less efficient, less power etc.Since Peter lives at elevation, 85 octane is the equivalent of 87 at a lower altitude so the engine should work the same.

[ftf]

Since Peter lives at elevation, 85 octane is the equivalent of 87 at a lower altitude so the engine should work the same.

This isn't true for Turbo cars actually. Since the turbo is pumping however many PSI of air in to the combustion chamber, the effect of higher altitude is negated.

Edit: this is also why turbo engines at altitude loose less power than NA cars at altitude.

Edit2: What is 85 octane, and is it safe to use in my vehicle?

The sale of 85 octane fuel was originally allowed in high-elevation regions—where the barometric pressure is lower—because it was cheaper and because most carbureted engines tolerated it fairly well. This is not true for modern gasoline engines. So, unless you have an older vehicle with a carbureted engine, you should use the manufacturer-recommended fuel for your vehicle, even where 85 octane fuel is available.

https://www.fueleconomy.gov/feg/octane.shtml

[Richard]

First, I would assume that your VW is a premium gas engine. Running 85 octane will do it no good over the long run. Second, make sure whatever gas you use has a detergent package. It will prevent fuel injector problems and carbon buildup on the valves. Third, if one brand uses ethanol and the other doesn't, the ethanol cuts mileage by about 5% if it is a 10% blend. Ethanol raises octane, but is lower in BTU per gallon than gasoline so mileage will suffer.

[shovelhd]

VW recommends against using E85 in all of their engines. I'd stick with 87. No need for premium for that model.

[Mikej]

VW recommends against using E85 in all of their engines. I'd stick with 87. No need for premium for that model.

i agree -

[eddief]

It has only ever seen 87 since the day it was born. Over the last 2000 miles in very mixed but maybe more city driving, the computer now shows 25.8 mpg. I drive like spirited old fart.

[Ralph]

Believe he's using hi altitude fuel. Climbing long steep hills at relatively low RPM. If a car will ping or pre ignite....those are conditions it will do so. His 85 mountain fuel like our 87. His 87 almost like our 91.

As above have said.....when/if your knock sensors detect pre ignition they will pull timing. Then you make slightly less power. Maybe use slightly more fuel for same power output....maybe not...maybe just less power. However....if your owners manual recommends 87.....your mountain 85 is equivalent to that. If you wish, just use the local 87 if car does better. Just remember.....even if not measurable.....higher octane fuels have slightly less energy (BTU's) content.....higher octane fuels don't ignite as easily and quickly as the piston comes up (increasing pressure and heat).....chemicals are added to reduce the volatility (and BTU) of the fuel to prevent pre ignition.....so in theory.....you always want to run the lowest octane fuel your engine can use. Turbo 4's add pressure to cylinders (atmospheric plus added turbo boost....or pressure), so in theory....your vehicle will need a lower volatility fuel than a naturally aspirated engine. Modern electronics perform miracles in reducing timing under these increased cyl pressures, but give up power output to do so. Whether theory plays out in a relatively unstressed relatively low HP engine is another subject. (Ford's 4 cyl 2.0 L race Turbo engine makes 1000 HP reliably...for a race anyway....needs all the octane it can get)

If I were entering a gas mileage (MPG) contest in Boulder in your car....for sure would use 85. Would avoid Pre ignition using throttle lightly.

[thwart]

Geez, maybe it's because I've been driving my wife's Prius too much...

My gas mileage has been better than some have quoted here. 2017 GSW, 4-motion, 6 spd MT. Never less than 30 mpg (calculated, not from the MFI), with around 3500 miles on the car at this point. Overall average so far 33 mpg... but to be fair, half of that was a long road trip. Obviously it's really too early to say what the car will do over the long run.

I'm cheap, so far about 50/50 use of mid-grade and regular gas. Can't really say I've noted a difference.

I drive like spirited old fart.I guess most of the time, I don't.

But I sure do ride my bike that way. :banana:

[CaptStash]

So here's the thing about mid-grade, it's one part premium, to two parts regular. That means that they are sticking it to you at the gas station, since it is almost always priced exactly half-way between regular and super. How do I know? I used to mix the stuff up 35,000 barrels at a time (that's 1.5 million gallons) running between Corpus Christie and Tampa.

so if you have to use mid-grade, guess at how much gas you need, then divide by three and put that much premium in, followed by filling it up with regular. The whole mid-grade thing still annoys the crap out of me.

CaptStash....

[pbarry]

Peter, are you figuring mpg with a pencil and paper, or a calculator? The dash mpg readout can be off by a few mpg.

[pbarry]

VW recommends against using E85 in all of their engines. I'd stick with 87. No need for premium for that model.

I know you know this. ;) But before we get really confused: E85 is a high percentage ethanol fuel, also known as flex fuel. 85 vs. 87 octane conventional gasoline​ is the debate. Carry on. :beer:

[jumphigher]

So here's the thing about mid-grade, it's one part premium, to two parts regular. That means that they are sticking it to you at the gas station, since it is almost always priced exactly half-way between regular and super. How do I know? I used to mix the stuff up 35,000 barrels at a time (that's 1.5 million gallons) running between Corpus Christie and Tampa.

so if you have to use mid-grade, guess at how much gas you need, then divide by three and put that much premium in, followed by filling it up with regular. The whole mid-grade thing still annoys the crap out of me.

CaptStash....

Interesting. Thanks for posting. :)

[Ralph]

Some reasonably accurate discussion of 85. However....like I said above, if it runs better on mid grade....87 in your area....run that.

https://community.cartalk.com/t/gas-octane-high-altitude-areas/87747

[eddief]

34 mpg. Probably never see that again.

[dustyrider]

So here's the thing about mid-grade, it's one part premium, to two parts regular. That means that they are sticking it to you at the gas station, since it is almost always priced exactly half-way between regular and super. How do I know? I used to mix the stuff up 35,000 barrels at a time (that's 1.5 million gallons) running between Corpus Christie and Tampa.

so if you have to use mid-grade, guess at how much gas you need, then divide by three and put that much premium in, followed by filling it up with regular. The whole mid-grade thing still annoys the crap out of me.

CaptStash....

Are you talking 87 or 89? Cause I haven't seen 85 outside of Colorado much. We've got 85, 87, 91(92/93). Everyone else has 87, 89, 91(92/93). I sure can see 89 being a mix as you describe, but not 87.

[CaptStash]

Are you talking 87 or 89? Cause I haven't seen 85 outside of Colorado much. We've got 85, 87, 91(92/93). Everyone else has 87, 89, 91(92/93). I sure can see 89 being a mix as you describe, but not 87.

The heck if I remember. Probably 87/89/91 but it was 1993 give or take; a lifetime ago. I was done with clean oil and went back to the crude oil biz in 1995.

CaptStash....

[dustyrider]

The heck if I remember. Probably 87/89/91 but it was 1993 give or take; a lifetime ago. I was done with clean oil and went back to the crude oil biz in 1995.

CaptStash....

Ahh...when gas was under a buck a gallon! :cool:

[CaptStash]

Ahh...when gas was under a buck a gallon! :cool:

Not THAT long ago!

CaptStash....

[dustyrider]

Not THAT long ago!

CaptStash....

I bought gas in the late 90's for $1.11. Just figured it had to be cheaper in early 90s.

[CaptStash]

I bought gas in the late 90's for $1.11. Just figured it had to be cheaper in early 90s.

I just Googled it. You're right. I must be getting old....

CaptStash....

[Ken Robb]

Here's a laugh for you all: in the summer of 1960 I drove from Chicago with 3 pals. There were "gas price wars" across Kansas and into Colorado. Regular gas got down to 17.9 cents per gallon. :-)

[oldpotatoe]

First, I would assume that your VW is a premium gas engine. Running 85 octane will do it no good over the long run. Second, make sure whatever gas you use has a detergent package. It will prevent fuel injector problems and carbon buildup on the valves. Third, if one brand uses ethanol and the other doesn't, the ethanol cuts mileage by about 5% if it is a 10% blend. Ethanol raises octane, but is lower in BTU per gallon than gasoline so mileage will suffer.

No, 'mid range' octane via the manual..87 octane, not 'premium'. ALL gas in CO is 10% ethanol, year round, now.

NOT E85..

[oldpotatoe]

Peter, are you figuring mpg with a pencil and paper, or a calculator? The dash mpg readout can be off by a few mpg.

Calculator..not the read out.

[paredown]

Here's a laugh for you all: in the summer of 1960 I drove from Chicago with 3 pals. There were "gas price wars" across Kansas and into Colorado. Regular gas got down to 17.9 cents per gallon. :-)

Our story that is similar is we got fired up to go to Nevada City to race--1972--so we drove our beater International Harvester panel truck from Vancouver to California. (A then-Junior Canadian bike racer named Ron Hayman was one of the passengers-later a founding member of the Schwinn-7-11 team.)

There was a price war on down parts of the coast and we were getting gas for $.25/gal--which was good because we had no money, and that old 6 in a heavy vehicle got terrible mileage...

Back on topic--I have always followed the manufacturer's recommendations--so the various Volvos and VWs that we have owned that have called for premium, that is what I have used. From what I have read, the slight improvement in gas mileage from premium about offsets the difference in price--and you don't run the risk (as with some of the Volvos that run hot already) of burning valves from predetonation etc.

[OtayBW]

Possibly a helpful article: https://www.edmunds.com/fuel-economy/to-save-money-on-gas-stop-buying-premium.html

and

Required reading(!): http://www.cartalk.com/content/premium-vs-regular-1

[shovelhd]

No, 'mid range' octane via the manual..87 octane, not 'premium'. ALL gas in CO is 10% ethanol, year round, now.

NOT E85..

Ok. I know it's a regional thing. In MA the only 85 octane I've ever seen is E85. It's rare around here. The lowest octane is 86 or 87.

My GTI requires 91. I've run 91 and 93. It has better low end power with 93, gas mileage isn't significantly different. Try a few tanks from the same station.

[Ralph]

At altitude.....with less atmospheric pressure....85 same as 87 at sea level. That's why they have 85 in Colorado.

At sea level....all vehicles have 14.7 lbs of boost from the atmosphere. If you add a turbo or super charger that adds 15 lbs of boost.....you are doubling the cylinder pressure.....causing fuel to want to ignite faster....possible too fast, and you can get pre ignition....so you need a less volatile (lower BTU of energy) higher octane fuel.

When you go to altitude, especially hi altitude, you have less boost from the atmosphere, so you can use a lower octane fuel.

[carpediemracing]

The Missus just did a road trip, 7 hours each way. The 2017 Civic, 1.5 turbo, 87 octane, wider +1 tires (245 vs 215mm, 18" vs 17" rims, but weight is overall the same or a bit lower than stock). 37-38 mpg for the tanks, one tank each way.

Not a lot of drafting/traffic. I remember in the TDIs we'd get in the mid-upper 40s (rated 40-41 mpg) doing the same trip but we'd have expected higher. We had to use a lot of throttle to maintain the higher 75-80 mph cruising speeds up north - speed limit is 80 mph for the last bit of 95.

On the other hand driving to Delaware/south on I-95 in NJ the traffic is heavy, steady, 75 mph. In the 350Z I'd get 33-35 mpg (rated 24 mpg?), in the Jetta wagon TDI we got 53-55 mpg.

So based on tracking mpg for the last 20+ years I figure that the 2017 Civic did really well.

[carpediemracing]

So here's the thing about mid-grade, it's one part premium, to two parts regular. That means that they are sticking it to you at the gas station, since it is almost always priced exactly half-way between regular and super. How do I know? I used to mix the stuff up 35,000 barrels at a time (that's 1.5 million gallons) running between Corpus Christie and Tampa.

so if you have to use mid-grade, guess at how much gas you need, then divide by three and put that much premium in, followed by filling it up with regular. The whole mid-grade thing still annoys the crap out of me.

CaptStash....

This reminds me of when I first started driving. I had a 1978 Datsun B210GX which used leaded gas. The way to boost octane substantially was to get whatever unleaded (zero lead, which boosts octane) and mix with leaded gas. Because the "untreated" unleaded was already whatever octane, the leaded gas would boost it a bunch.

I had no idea on how much lead was in a gallon of leaded but I vaguely recall reading about using 50-50 ratios so I'm pretty sure what's what I did.

For "really high octane" you'd get premium unleaded and mix with leaded regular.

This was back in the day of twisting the distributor a bit to advance the timing. I wasn't very good at documentation so I didn't track much of anything but I was always twisting the distributor a bit, if I heard knocking I'd stop and twist it back a bit. I also had a B210GX so my gains were probably close to the statistical noise in terms of horsepower levels.

Then, for a while, I read about naphtha, which is something like 115 octane raw (used by the some F1 teams in the old turbo days, 85% naphtha with 15% inert liquid for some reason I don't remember), this when I had a turbo car with a carb. But because I wasn't doing anything with the car it didn't matter much, engine started disintegrating long before I could get into whatever.

[oldpotatoe]

Thanks for all thee responses..even if a placebo, or whatever, I use what the factory recommends..mid-grade. Really love the car, BTW. Been stuck in traffic on I-70 on the way to the ginormous CU hospital in Aurora..having the DSG is nice.

[CaptStash]

This reminds me of when I first started driving. I had a 1978 Datsun B210GX which used leaded gas. The way to boost octane substantially was to get whatever unleaded (zero lead, which boosts octane) and mix with leaded gas. Because the "untreated" unleaded was already whatever octane, the leaded gas would boost it a bunch.

I had no idea on how much lead was in a gallon of leaded but I vaguely recall reading about using 50-50 ratios so I'm pretty sure what's what I did.

For "really high octane" you'd get premium unleaded and mix with leaded regular.

This was back in the day of twisting the distributor a bit to advance the timing. I wasn't very good at documentation so I didn't track much of anything but I was always twisting the distributor a bit, if I heard knocking I'd stop and twist it back a bit. I also had a B210GX so my gains were probably close to the statistical noise in terms of horsepower levels.

Then, for a while, I read about naphtha, which is something like 115 octane raw (used by the some F1 teams in the old turbo days, 85% naphtha with 15% inert liquid for some reason I don't remember), this when I had a turbo car with a carb. But because I wasn't doing anything with the car it didn't matter much, engine started disintegrating long before I could get into whatever.

I had a '74 V6 Capri boy-racer and did my share of distributor twisting to get things just right. I loved getting a tank of Sunoco 102 for nights on Mulholland.

Interesting that you mention Naphtha, which literally has no precise definition in petroleum land. We carried stuff labeled "Naphtha" that ranged from nasty raw semi-refined gasoline, to garden variety regular. It's a catch-all term. It's also good to understand that there is little difference between brands of gasolines. Just because you might buy Chevron gasoline, has nothing to do with who refined it. The only difference is in the additives, and nowadays, there is little difference there either.

CaptStash....

[Ken Robb]

Thanks for all thee responses..even if a placebo, or whatever, I use what the factory recommends..mid-grade. Really love the car, BTW. Been stuck in traffic on I-70 on the way to the ginormous CU hospital in Aurora..having the DSG is nice.

I read some reports that creeping along in stop and go traffic is hard on DSG and other dual clutch transmissions. I can see how this might be true because when you ease on the gas from a stop the clutch engages partly (like you would driving a stick) but if you can't get up to some pre-set minimum speed the clutch can't fully engage so you ease along with a slipping clutch.. I suppose if traffic allowed you could try to be either fully stopped or accelerating briskly past walking speed to minimize the time of partial engagement.

A good pal runs a driving school. He had a couple of VW diesels with dual clutch transmissions and neither one of the trannies lasted much past 100,000 miles. He is very careful with maintenance (so much so that VW helped pay for new tranny even though warranty was up) but we can imagine that teaching beginners to drive would have cars doing a lot of start/stop ease-along driving.

[carpediemracing]

One other thing about E85. You can use more of it if your car knows to take advantage of it. If so it can make more power. Reduces economy though.

https://grassrootsmotorsports.com/articles/fuel-truth/

93 octane pump gas (10% ethanol): 136 hp, 124 lbs/ft
87 octane pump gas (10% ethanol): 135/117
93 octane (0% ethanol; best for long term storage): 134/122
E85: 143/128
100 octane race gas: 137/123
105 octane race gas: 137/124
Methanol: 160/140

E85 has more oxygen in it. However you needed 63% more in the experiment above, so your mileage would drop by, what, like 1/3?

100 octane gas required 2% less fuel, so your mileage would go up a hair. 105 octane used 4% less fuel.

Methanol is really bad for your car, requires about twice as much fuel, but makes gobs of power.

[shovelhd]

I'm sure that creeping isn't good for a DSG, so I minimize it whenever I can. I drive it like I drove my stick. The DSG in my 2009 has an extended warranty until 120K miles or ten years.

[choke]

Here's a laugh for you all: in the summer of 1960 I drove from Chicago with 3 pals. There were "gas price wars" across Kansas and into Colorado. Regular gas got down to 17.9 cents per gallon. :-)I can top that. :) A small town near where I grew up had two gas stations which were across the street from each other. One day in 1986 one of the stations lowered their price to match the other so the other responded by lowering it 1¢ below that. They went back and forth, each lowering their price until finally both stations were giving gas away for free. They did impose a 10 gallon limit on the free gas.

The war began Tuesday when Star chopped a penny off its prices to match Huck`s.

At 9 a.m. Thursday, both stations were selling regular for 48.9 cents and unleaded for 53.9 cents. By noon, it was down to 12 and 13 cents before a series of quick changes brought it to zero.

http://articles.chicagotribune.com/1986-06-27/news/8602150817_1_huck-stations-zero

[thwart]

Been stuck in traffic on I-70 on the way to the ginormous CU hospital in Aurora..having the DSG is nice.
Hey, driving through Atlanta (post I-85 freeway bridge collapse) has to be even worse. The 6 spd MT has a light clutch and easy take-up. No problem at all.

Not to say the DSG isn't a good choice as well...