A question on 91 octane gas!Out here in So.Cal. we have several brands available (Union 76,Chevron,Arco,Shell,Valero)to name a few. Is any one brand better than another for your engine? A friend told me that you don't see the name of the brand on the tankers trucks anymore because they fill up at the refinery and deliver to what ever brand is on their route so you would be buying the same gas at Shell station as your local Arco but at a higher price! Any body working in this field shed some lite? Also,he's running a 427 Ford with solid lifters and fills his tank 1/2 way with 91 octane (Union 76) then fills the rest with 100 octane Aviation gas,says it performs better with this mix! I thought that aviation gas octane was figured differently then automotive octane,so is he really gaining any benefits by mixing or on the path to destruction?  Aaaah the curious mind! SKIP

I won't comment on the part about mixing av gas w/ pump gas.  Sounds alright but . . . . .

After 20 years in the oil and gas industry and some of that at a gas plant (ARCO), I will say your friend is correct about many different brand stations being serviced by a single refinery.  However, at the loading station, the refineries add chemicals in the ratio specified by the corporate folks (detergent,etc.).  There truly is a difference then in what comes from the pump.  I have been told in private that in the Austin/Waco area Phillips 66 supplies the poorest performing high octane and Citgo the best.  This was not determined by chemical analysis but by engine performance.

TC

You gotta have the right tools and know how to use 'em.

TC - Austin, Texas

The 100LL aviation fuel does help the octane number but it’s not race fuel either and burns drier than regular fuel.  Racers in this area are still trying to get by with this fuel on 12½:1 compression ratio and the effects from detonation are still apparent.  But for an engine running up to 11.0:1 CR, then aviation fuel would be a less expensive alternative keeping in mind that it does burn drier and the use of some Marvel Mystery oil or something similar will help both the electric fuel pump and the engine.

Lorena, Texas (South of Waco)

 Been a fuel tanker driver for 18 years and it is as Tom said it is not the base stock, it's the different additives and quantities used in the "brew" that makes them different. Even to the extent that brand X smells different to brand Y. It's much the same with oil too. Here in Aus. with each capital city only having one or two refineries they all supply each other. The big 4 are Shell, BP, Mobil and Caltex with unleaded octane rating being 91, 95 and 98. Shell does have a pump 100 but it is only available at a few site in the capital cities.  The company I drive for has some "branded" trucks, majority are  not, so you can do different brand sites. You get some funny looks when you are delivering to a Mobil site in a Shell truck!!     

Pete, one of the Aussie mob. Beechworth, Victoria60 F100 Panel Van, Y-block. 65 Galaxie Country Sedan 390

Back in the day (70's and early 80's) when I was doing the round track thing with a scrub, we ran a 50/50 mix of 110 avgas and premium gas with two cans of marvel mystery oil per 55 gal drum. Worked pretty good for race purposes, but would be expensive for street use.

Glen Henderson



Freedom is not Free

Letohatchee, AL

Tom,

           That's good info, doubt if most of us knew that, I had no clue, thanks.

Frank/Rebop

Bristol, In ( by Elkhart) 

On the circle tracks in west Texas a lot of "street stock" cars ran on a 60/40 mix of regular leaded/unleaded. Octane result was about 105 by adding the lead back into the unleaded. Worked for us! Chuck in NH

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

In Indiana we can still buy 110 octane, actually up to 118 octane leaded "racing fuel". I am told the tractor pullers run it. The leaded 110 octane is around $30 for 5 gallons. Also available at the drag strips in their pumps.

   There's a number of additives that you can get at Autozone, etc. will help the valve wear issue. "lead" is not the only chemical that will reduce valve seat erosion. Also, remember, we don't usually have to de-carbon the heads much any more, so it's not all bad.

Frank/Rebop

Bristol, In ( by Elkhart)