What kinda gas do you use?

[Razorback1980]

Ken, show your class and style and make sure you always play well with others. You may need thier help someday.

[Ken99287]

hey i wasn't being mean, just joking and poking a little fun, that's all

[Ken99287]

i am glad to get this conversation going again though because with gas prices so high, i don't want people paying extra and not getting anything out of it. now if it actually helps(higher compression vehicles, forced induction, etc), go for it! i used high octane with iso in my saab because it really boosted performance. It just bothers me that some people think that even though their car calls for low or mid grade, that somehow high grade will give them better results. that's like, being tricked by the gas companies! i mean, they charge us enough already, we don't have to fall into their, do you want "Low" grade or "Performance/Ultra/Premium" trap.

[Keithr726]

91

[B. Elliott]

Originally posted by Ken99287
i am glad to get this conversation going again though because with gas prices so high, i don't want people paying extra and not getting anything out of it. now if it actually helps(higher compression vehicles, forced induction, etc), go for it! i used high octane with iso in my saab because it really boosted performance. It just bothers me that some people think that even though their car calls for low or mid grade, that somehow high grade will give them better results. that's like, being tricked by the gas companies! i mean, they charge us enough already, we don't have to fall into their, do you want "Low" grade or "Performance/Ultra/Premium" trap.

It's not an issue of boosting performance, it's a matter of what is required to keep the engine from detonating. Like I said before in my pervious post, using a higher octane gas than what is required will cause an excessive amount of byproducts to be formed after combustion.... leading to carbon buildup and dead converter.

When i had my old '65 Impala i had no choice but to use 92 or 93. Anything less and it would ping. Jumping up to race gas would do nothing for it. In theory, and actual use.

[B. Elliott]

Originally posted by AaronM
Factory recommendation is in RON, not US AKI. RON 92 = US AKI 87. US is (RON+MON)/2 and is typically equivalent to a Euro rating 5-6 points higher.

I ran 87 octane in my '89 944 NA (10.9:1 CR) and it didn't ping at all. Also did just fine on mileage.

Well, looks like i'll have to dip down to some 87. I was never aware of the octane rating differences. I thought Porsche would have listed it in AKI for the US owners manuals... guess not.

[Ken99287]

B. Elliott, i know octane is not about increasing performance, i'm saying that in my saab, because it didn't ping, it allowed me to have increased performance(knock sensor). See??? i already posted that it's not about performance, and that the higher the octane rating, the less likely the fuel mix will preignite. i realize that the higher the compression, the more likely the fuel mix will preignite. just use whatever the manufacturer says to use, of course using the correct units. technically, the higher octane fuel produces less energy, but not significantly or noticably... diesel, with an octane of what..... 20's(or 40's?? i don't remember) has more energy than gasoline but is very easy to pre-ignite, that's why diesel engines don't use spark plugs, it just ignites itself as pressurized air enters the chamber- too high an octane and the engine may not run, too low, ping - no increase of performance.

Originally posted by Ken99287
just use 87, the high octane stuff is for cars with knock sensors and forced induction applications. example - using 87 in my saab only produced 18psi boost, but high grade produces 25(knock sensor lowers boost levels), that is because higher octane makes the fuel mix harder to preignite(ignite from being pressurized), ensuring that the mix only burns when the spark plug sparks. pre-ignition/detonation is bad because it's igniting during the compression stroke-very hard on engine parts. but regular cars only need the lowest grade needed to prevent detonation. the "Porshe" badge doesn't mean it's not still just a regular ol' combustion engine. just cuz it's a porsche don't mean high grade will do miracles. now if you had a 951...

[AaronM]

Originally posted by B. Elliott
Well, looks like i'll have to dip down to some 87. I was never aware of the octane rating differences. I thought Porsche would have listed it in AKI for the US owners manuals... guess not.

I'd say to try a small amount of 87 first, there is, after all, some variation between engines, even when mass-produced and age increases those variations. My dad had an Explorer with the Ford 302 V8, specs called for 87, but it would ping when hauling/towing with anything other than 91+, so we just always ran 91 (no-one could find any issues with the engine, so we just chalked it up to production variances).

[Schumi]

Originally posted by AaronM
I'd say to try a small amount of 87 first, there is, after all, some variation between engines, even when mass-produced and age increases those variations. My dad had an Explorer with the Ford 302 V8, specs called for 87, but it would ping when hauling/towing with anything other than 91+, so we just always ran 91 (no-one could find any issues with the engine, so we just chalked it up to production variances).

We had a early model (92 or 93) Ford Explorer model V6 that would not run well on anything but premium. When I say not when I mean bad pinging, from the day it was purchased Not only did it need premium but it was a gas hog even for a V6. It only got 18mpg. Talk about horrible...

[Ken99287]

to reduce pinging, i think you can.... retard the timing?? i think... or is it the other way around??? you can usually do a slight adjustment on the distributor... on some cars anyways.

[B. Elliott]

Originally posted by AaronM
I'd say to try a small amount of 87 first, there is, after all, some variation between engines, even when mass-produced and age increases those variations. My dad had an Explorer with the Ford 302 V8, specs called for 87, but it would ping when hauling/towing with anything other than 91+, so we just always ran 91 (no-one could find any issues with the engine, so we just chalked it up to production variances).

That is true. I may have to try a little bit once it's up and running again... ring and pinion went out. I have noticed one thing from experience though. After messing with a lot of honda and cadillac engines, i've seen instances where excessive amounts of fluffy (and hard) carbon buildup has caused a signifigant decrease in the combustion chamber volume... increasing the octane required to keep detonation at bay.

Driving around town at steady/low rpms will cause quite a bit of buildup.

Sometimes going WOT is actually good preventative maintenance.