blown 87

Unless the car is detonating on 93 putting a higher octane fuel in it will actually slightly knock a little power off.

Gasoline weighs around 6.0-6.7 LBS/Gallon depending on the specific gravity and temp, etc.
Higher octane weighs more.

I agree, get all the weight out you can.

RCinXS

Higher octane fuel will always create better acceleration and better gas milage in any car including a VW Beetle with 250K on it.

It will also make a car run smoother and clean the carbon out like nothing else.

With higher octane fuel, you do not have to push the pedal down as far as you would with lower octane fuel in any given situation.

This is all per the Shell Oil training program from some years back. If they are incorrect or have been proven wrong by another oil company, I apologize.

When I took these classes I did not beleive them either. But I tried it and assure you that I found all of the above to be true regardless of the car and it does make a huge difference.

I'm not saying that you should run this fuel every day. But in a flying mile, it will give you an edge.

Try it, you'll like it.

Larry Velk

The 60's Chevelles ('shovels', as called around here) had surprisingly good weight distribution. They were quick street cars back in the 70's. I spent about 10 years in a Chevy service dept back in the 70's and the fit and finish of the Chevelles was a bit better than other Chevies.
My bother-in-law ran a 289 Falcon with a 3:90 posi (9inch), scatter shield, internal balance, 351 heads (ported and cc'ed), headers and open exhaust. He could drive. Ran 13.5 at 103 - this is a very fast street car and had no problem with stock 455 Firebirds and such. Twelve second range on the street with old iron is hard to do. You need to be crazy, the car needs to hook-up and with the old stuff the details need to be correct. The bro-in-law is a tool maker (like out Green Bay wizard) and that Falcon was right on the money (he blew many 8 inch Ford rears 'till he got the 'Stang 9 inch). The shovel will have coils in the back with who knows what kind of detail work - he'll still kill you - but he may have a 14 second car in reality. Drag racing does involve some skill, especially with a bike - my GSXR 1100 was faster stock at Union Grove than many Chicago hot shots who ruined the Japanese tune with the wrong jets, etc. Go to the strip sometime - you'll see some surprisingly slow cars!

blown 87

You are incorrect.

When a motor is set up for a higher octane fuel with more compression, boost, ignition, etc it may need more octane, but there is less energy in one gallon of 100 octane than in one gallon of 80 octane.
Pretty simple stuff.

Some engines use knock sensors to advance the timing and they may gain from using a higher octane than say 87, but going from 93 to 103 is not going to do a thing in a stock 928.

ptuomov

Yes, higher octane gas will not help at all with a early model stock 928, since they don't have knock sensors. With a stock GTS on a really hot day maybe a little bit, since it has knock sensors and people say it knocks a lot on 93 on a hot day.

Here's a question: What would happen if you'd mix some nitropropane with your gas? My thinking is that many 928 models seem to run too rich in high-load, high-rpm cells. Just the right amount of nitropropane would lean it to just right and also make additional power on its own right.

dr bob

Many things that were true 'back in the day' are no longer correct. Additives like toluene and tetraethyl lead are now verboten due to cancer concerns and emissions worries, replaced first by by MTBE and now ethanol. Thank ADM and their lobbying for corn fuel subsidies for the costs and effects of diluted fuel.

Ethanol is extremely hygroscopic and causes corrosion in unprotected metal fuel pipes, is tough on the original flexible fuel lines, and has a fraction of the available energy per pound that the rest of the gasoline has. The density of ethanol is greater than gasoline, so a gallon of premium with ethanol weighs more than a gallon of non-diluted gasoline. So you get a heavier gallon that doesn't have as much total energy, costs more, and chews up the fuel system pieces. The original calcs for emissions were based on pounds of spewed components vs pounds of fuel used, instead of the more logical mass-per-mile number that would take into account the poorer performance.

As an example, I drove to DFW for the OCIC a couple summers ago. 19 MPG at barely super-legal cruise on SoCal fuel blend, until we fueled in Flagstaff. The higher-altitude blend, without the 'oxygenating' ingredients required in major metro areas, jumped the mileage to over 22. It stayed up through the tank in Alamagordo, fell off with 100+ touring with the red run group into Texas, and then back to "normal" with metro DFW oxygenated blends again. Modern high-test is crap, except it's all we can easily buy that the engine will run on without detonation.


My history includes a stint as an intern with Standard Oil of California in the early 1970's, working on engine tunes and fuel blends that would allow GM cars to meet the tightening tailpipe standards. Fuel injection and serious electronic ignition were a direct result of a lot of those early efforts. Lead was out because of the catalysts, toluene was still in there.

blown 87

A little to much and you might need a broom and some oil dry.

ptuomov

How do you ever know where the edge is without stepping over it? ;-)

I guess the wideband lambda sensors would work with gasoline-nitropropane mixture. So if one were serious about this, maybe one could swap in bigger injectors and then up the nitropropane percentage until the lambda sensor reads rich best torque.

Sounds like nice high school science project (if you last name is Walton or Buffett.)

blown 87

http://www.nitrobahn.com/nitro-barn/...mileage-power/

RCinXS

Wow. No mention of higher octane fuel burns slower and more evenly than low octane? (That's why the knocks go away)

I wonder why the Porsche manual says a minumum of 93 octane with nothing about going over?

RCinXS

I'll just leave you guys to all this theoretical stuff and keep doing what I already know works for me in my old shark for the last 24 years without exploding or even having a puff of smoke from the exhaust.

See Ya.

blown 87

Because that is what the engine was designed for.
I have built up enough hot engines to know how to figure out about what octane is going to be needed.

Believe us or not, it does not change the facts.

I also do not doubt your supercharged car runs better on 103 than 93, but that is a whole nuther ball game there, you have increased the effective compression, the BMEP, and other things, and need a higher octane.

A stock OB does not need it, nor will it help it.

If it works for you, by all means use it.

ptuomov

EDIT: What he said ^^^

If the engine is correctly tuned to produce best power with pump 93, then switching to fuel that is similar in every other respect except that it burns slower will reduce power.

I think that this is because there is no danger in going higher octane. Maybe a bit higher exhaust gas temperatures, but that's not a big deal.

Perhaps you have too much spark advance for pump 93 and that's why slower burning fuel works well for you. Just one possibility.

I am curious, though: How you have documented the increase in power with higher octane fuel?

blown 87

Exactly, if it runs better with 103, then it is not tuned right to run with 93.

I also wondered how he documented the change in performance.

James Bailey

No doubt the highly objective finely tuned assometer.....it is hard to undo so many years of oil company advertising. Knowing that car lovers are not objective and WANT to do nice things for their car using premium fuel just SOUNDS so much better than regular There are in fact slightly more cleaning additives in some of the high priced spread but all grades of fuel MUST have a minimum acceptable level to be sold in the U S.