I believe it was recently in my local newspaper it was mentioned that even for cars whose manuals recommend higher octane fuel those people who used regular experienced no difference. I'm interested in finding out more. Has anyone experimented with different octane ratings? Any links to studies done or similar articles? Pretty much any comments at all regarding the usefulness of higher octane fuel.

 

unless you have bumped up timing or forced induction, or maybe nitrous, regular is all you should run. running anything higher will have no benifit. If the manual recomends a higher grade, it maybe be due to the fact that the timing is higher. Run whatever the manual says

 

Yea, you need higher octane if compression is higher, due to either forced induction, higher CR, or advanced timing. Also, on old and tired engines, deposits from EGR and other old stuff could lead to preignition, in which case you'd use a higher octane also. If you have stock car there should not be any difference between running an 87 and 93. Contrary to the popular believe 93 and 87 burn the same way and speed.

Now as far as power difference goes on a non stock naturally aspired car, between 87 and 93, it could mean as high as 50 rwhp, depending on CR and the type of ignition used. Even higher than that in all out racing.

 

Yup. It can make a big difference in engines built for performance.... I can cut almost 2/10ths of my lap time when I run 110 leaded as opposed to reg. 94 in the kart. Every little bit helps.

Jim

 

Most of the engines that require higher octane ratings can be safely run on lower octane rated fuel IF you don't run the engine hard.The four valve 4.6 engines have a knock detector and will pull timing if detonation is detected while running lower octane fuel or engine conditions cause detonation.If you want to experiment,run the car down to around 1/4 tank and add about five gallons of lower octane fuel.If you get no detonation on this blend,run it down to about 1/4 tank again and add five more gallons.If this gives no problems go ahead and fill up with the lower octane.The reason you only fill to about 1/2 tank is if you get detonation you can fill the tank with higher octane and raise the octane rating of the remainder of the fuel.Remember,this is just enough octane to pull the car along at cruising speed not a high performance solution.Going up hills can also cause problems so be sure to test for this also.

 

it's nice to see that more people seem to understand that premium fuel is not required and does not make any difference in the performance of "normal" stock vehicles. If your manual does not specify using high octane fuel, then save your money because the car was designed and tuned to run on lower octane fuels. In fact, since higher octane fuels are more resistant to combustion, you may not be burning all the fuel in your combustion chamber which is bad for a number of reasons.

 

Preignition happens alot more when cruising at 1/4 throttle, alot of race cars will detonate bad if run at 1/4 throttle but will stop when more throttle is applied because more gas is then injected.If you do notice detonation on hills just apply more throttle and it will usually stop

 

in the older SVO they acually had a switch in the car that went and changed the ecu from 87 octane to 91 i believe. this way you could have a higher performance fule or just run regular.

 

That is a seriously misleading myth. Higher octane fuel is resistant to cumbustion alright, but not in the way you think it is. It resists compression (and thus heat). It ignines just as easily as lower octane, it burnes with more intensity but flame is propagated at the same speed. You will not be hurting anything if you run higher octane pump gas.

Now as far as racing fuel goes, if octane is really high you might burn some gaskets and rings if engine is not repared for it with CR and timing to extract the extra heat.

 

"Race gas"or any other high octane fuel for that matter,has the same btu value as any other gas.It's the molecular build of the fuel that resists detonation.There's two kinds of "pinging"that you worry about.The first one is detonation.It's caused by the fuel exploding instead of burning.This is caused by too high of a compression ratio or too early spark timing.The second is pre-ignition,and is caused by hot spots in the combution chamber.This can be caused by carbon deposits,overheated valves,or too hot of a spark plug.If you are trying to save money by running cheaper gas on your trip to work,then running 87 octane would be the way to go.Just remember,listen for the sounds of pinging.Unless your exhaust or stereo is ultra loud you will be able to hear it.