87 octane vs 89 octane

[kill-9]

For me I don't ping on either octane, and I do feel the increase in power right away. But most importatnly it looks like I get better millage without any adjustments, and thats what I'm going for. I'll try it and see.

[ih freak]

Originally Posted by ATaylorRacing

Here is my take...with 35 years of drag racing street driven cars:

If your car does not require premium and the timing is stock you can actually get worse mpg with higher octane, The higher the octane, the slower it burns....a lot of cars drag raced with premium fuel will actually run slower and have less power. Just run reg if your car calls for it.

As far as running 87 in a car that requires 92.....on my 05 SRT4 Neon (230 hp 2.4 turbo bone stock) I WAS running 87 when I first got it. On my 80 mile loop that I use for mpg comparisons I got only 27 at 55-60mph while it was rated at 31. I even fill up at the same pump and put it on slow speed till it clicks off...not a penny more...then with 92 oct I then got the 31. That car now gets 32.8 with a stage 3 set up that developes 285 hp!

As far as 10% ethenol is concerned.....you might get as bad as 20% WORSE mpg since more fuel is needed to obtain the same driving parimeters. I read in a magazine last year that E85 can be as bad as 27% worse than straight gas and on my flex fuel 01 Caravan it did get @ 25% worse on E85 compared back to back with reg 87 oct gas.

Guys that convert their drag race cars to alcohol must increase the jetting in their carbs by about double for the same power levels, but then they benefit from a cooler running motor and can mofify them to run more compression and or boost.

I agree. I have a 95 volvo 850 wagon. If I run 87 in it in a matter of minutes I will stall at every stoplight or stop sign. If it calls for 87 run 87. If it calls for 89 run 89. I work in a small engine shop and we have seen a lot of engines vapor locking on hot days due to the lower boiling point of ethanol.

[tjts1]

I have a 96 volvo 850 wagon with 195k miles on the odometer. The owner's manual calls for at least 91 octane. I run it on 87 octane almost exclusively after testing every octane I could find repeatedly over multiple fill ups. There is no difference in power and a slight improvement in fuel economy with 87 octane. If you 95 volvo stalls on 87 octane, there is something else wrong with your car. Probably the thermostatic intake mechanism.

[nemesis]

Originally Posted by SVOboy

I don't think it would have adverse effects, but most people who use a different octance will report lower FE...then again, every car is different.

Lets see, adverse effects would be, lets think, fuel burns slower, timing is the same, so we get fuel left over, right, you following me so far, and unburned fuel turns into what??? I know you know this, carbon. And carbon deposits do what? Make the engine run less efficient Or so they say. I say carbon deposits on pistons would raise the comp ration, which will make it run more efficient, but you would need higher octane.

[nemesis]

Originally Posted by ATaylorRacing

Here is my take...with 35 years of drag racing street driven cars:

If your car does not require premium and the timing is stock you can actually get worse mpg with higher octane, The higher the octane, the slower it burns....a lot of cars drag raced with premium fuel will actually run slower and have less power. Just run reg if your car calls for it.

As far as running 87 in a car that requires 92.....on my 05 SRT4 Neon (230 hp 2.4 turbo bone stock) I WAS running 87 when I first got it. On my 80 mile loop that I use for mpg comparisons I got only 27 at 55-60mph while it was rated at 31. I even fill up at the same pump and put it on slow speed till it clicks off...not a penny more...then with 92 oct I then got the 31. That car now gets 32.8 with a stage 3 set up that developes 285 hp!

As far as 10% ethenol is concerned.....you might get as bad as 20% WORSE mpg since more fuel is needed to obtain the same driving parimeters. I read in a magazine last year that E85 can be as bad as 27% worse than straight gas and on my flex fuel 01 Caravan it did get @ 25% worse on E85 compared back to back with reg 87 oct gas.

Guys that convert their drag race cars to alcohol must increase the jetting in their carbs by about double for the same power levels, but then they benefit from a cooler running motor and can mofify them to run more compression and or boost.

You do need 20% more e85 than regular gas, which why some people hate it, but man it's great for forced induction cars, e85 is like racing fuel only half the price

[ih freak]

Originally Posted by tjts1

I have a 96 volvo 850 wagon with 195k miles on the odometer. The owner's manual calls for at least 91 octane. I run it on 87 octane almost exclusively after testing every octane I could find repeatedly over multiple fill ups. There is no difference in power and a slight improvement in fuel economy with 87 octane. If you 95 volvo stalls on 87 octane, there is something else wrong with your car. Probably the thermostatic intake mechanism.

Is your 850 turbo or non-turbo? Mine is the non-turbo. I love the car though...300 thousand miles and still ticking.

[Frank Lee]

As far as 10% ethenol is concerned.....you might get as bad as 20% WORSE mpg since more fuel is needed to obtain the same driving parimeters. I read in a magazine last year that E85 can be as bad as 27% worse than straight gas and on my flex fuel 01 Caravan it did get @ 25% worse on E85 compared back to back with reg 87 oct gas.

Kind of a leap to conclude that if E85 (roughly 85% ethanol) drops fe "27%" that E10 (roughly 10% ethanol- 75% less than E85) yields only 7% different results??? I've never experienced anywhere near a 20% fe drop because of E10.

[some_other_dave]

Originally Posted by nemesis

[Higher-octane] fuel burns slower ...

Not strictly true. In fact, I know several petrochemical engineering types who insist that the flame-front speed is more dependent upon cylinder pressures and mixture than upon the fuel composition. At least, in any gasoline we would see sold for street use. (Ethanol will change things; I am not sure how much.)

As a counter-example, there are known cases of aviation engines who suffered burned exhaust valves from running 110-octane Av Gas when they were designed specifically for 80-octane Av Gas. Those seem to have been caused by the mixture still burning as it exited through the exhaust port. But that's a much larger change in octane than we see in streetable motor fuels, and Av Gas is not really the same as automotive-grade gasoline.

-soD

[MadisonMPG]

Sometimes older engine need higher octane because of carbon build up.

[MadisonMPG]

Originally Posted by nemesis

You do need 20% more e85 than regular gas, which why some people hate it, but man it's great for forced induction cars, e85 is like racing fuel only half the price

Just get all of it out of the lines after teh race.