I've heard of a few racers who mix race gas 50/50 or so with straight, unleaded non-ethanol 87-octane pump gas.

Anyone here do that? Why do you prefer the mixture?

For years I've been running 91-octane pump gas in my Chevy 350 engine with, I suppose, around 9.5:1 compression and aluminum heads.

I have been told by a racer in the pipeline fuel delivery industry that semi-truck tank drivers who deliver to gas stations will dump leftover regular unleaded into the premium tank, effectively diluting it.

This race season I want to try using a mixture of race gas and straight unleaded fuel.
I don't want to spend quite that much money for straight race gas for my lower-compression engine.

I've been told that race gas is more consistent and burns cleaner. The engine just runs better, some say.

What might be the caveats? Would I need to advance the primary ignition timing?

I have a fuel/air gauge installed, with an oxygen sensor (which I have found to be useless anyway).

Thanks, guys
Troy

first, I would throw that air/fuel gauge in the weeds.

second, I ran pump gas for many years heard all the myths, rumors and hearsay and never saw an issue on the time slip as far as performance and consistency.

At 9.5:1, straight pump gas is all you need and want, anything more is a waste of $.

I have never done this but I have a close friend that is a retired scientist and he has always done it. Something like 5gal of pump gas to 1 gal of 110 race gas. Says he needs the race gas for the lead which raises the octane. True?, I don't know but he has some pretty fast cars and I have seen him mix it.

Here is an octane calculator for mixing:

Mixing Calculator

I've done it. Of course, I always start out with premium pump gas, because octane wise, it is actually a bargain. Same with the race gas to be mixed. Get the hottest stuff available, if you are shooting for a particular octane mix and want to keep the cost down (you can use much less of the higher octane to achieve your result). Another plus for the race gas is that it is leaded. If you happen to be running some really old cylinder heads without hardened seats, there is your lead to keep them living longer.

The engine I am using now doesn't really "need" more than premium pump gas, but I like having a little extra cushion and I like the lead. One gallon mixed with 5 pump gas gallons is more than enough for my peace of mind. Take care. Tom Worthington

We mix 1/3 110 VP with 2/3 93 octane pump gas. Small block Chevy with about 11.5 compression. Never a problem.

I have a 383 FT SBC. I started out at 50/50 93 and 110. I now mix 4 gal 93 and 1 gal 110 for peace of mind, no issues.

I missed for years. Made two stops for gas. Once for a gallon of Turbo Blue in each gas can and at the Sunoco station to top off the cans. This was on a 11:1 engine. Now I just run the 93 octane.

At your compression ratio and with ally heads you don't need the leaded stuff at all.

I forgot to add. 93 octane has a shelf life. After a week or so in plastic jugs it changes colors. What's left over from a race goes into the daily driver, lawn mower, chain saw, you get the picture.

With 9.5 compression you probably do not need the race gas anyway.

at 9.5:1 with race gas you are just sending cash out tail pipe.Heck I run 91 in street rod and harley and both are over 11:1.

Now it you have older heads that don't have harden seats then adding lead or mix gas with lead isn't bad idea. Lead additive is 5 bucks and treat 25 gallons so 20 cent per.

quote:

Originally posted by wideopen231:
it you have older heads that don't have harden seats then adding lead or mix gas with lead isn't bad idea. Lead additive is 5 bucks and treat 25 gallons so 20 cent per.

another myth perpetuated for decades by those that read it in a magazine.

ABSOLUTE BULLSHYT!!

when it comes to bullshyt know one knows more than ED!

id run ethanol-free 90 oct marine gas in that motor . . .and if its the smell yer after ? . . put some fragrance in it ! .lol

I run pump premium in a 357 at 12.7 CR. 235 cranking compression. No issues so far using aluminum heads.

I tried running pump premium at 14.5 CR with iron heads and broke a ring land. That was with same cam and crazy cranking compression.

If I was running 1/4 mile or when extremely hot, I would add 10% 110 to be safe. I have in a pinch added generator gas with no loss of performance.

quote:

Originally posted by wideopen231:
when it comes to bullshyt know one knows more than ED!

the TRUTH and the FACTS are you are broke dyck that is CLUELESS evident by the POS you built.

Truth and facts according to buy back king. Worth zero.

Don't worry Ed there is still a chance you will learn to build something besides Hemorrhoids. Like you its small chance.

apologies to OP for my part in another Ed derailing. End of conversation

must be true, I read it on an internet forum posted by a clueless, jealous, nobody with a POS that couldn't buy a round on his best day at my home track, no mind trailer me.

quote:

must be true, I read it on an internet forum

How most feel about your posts

Ran a 496ci BBC on pump gas, 93 Octane Sunoco. Tried mixture of 110 race gas. The only difference I saw was a lighter wallet. It was a 20% mixture of 110/93. No gain in performance. Don't waste you $$$$.

If your car is running the number on straight pump, I wouldn't spend the money on race fuel. Log your ET and your predictions (even for time runs) and see how you're matching up. If you're off a little, and want to try it, I'd suggest 4 gallons 91, 1 gallon 110.

I've always run straight 93 octane Sunoco. My '69 Cutlass has always been iron heads, around 10.5:1, never had an issue with it, car did everything I expected it to for ET. My '81 I'm running now, I'm mixing in the same manner above, more to be safe, especially in the hot summer months. I think the biggest thing with pump gas is to get it from a good quality station, preferably the same one every time, that has good traffic, so at least in the theory, the fuel is constantly refilled and fresh.

I tried mixing 50/50 blend of 110 race gas and pump premium, about 20 years ago, with a 10.24-1 BBC. It made the exhaust smell like shyt, and did nothing for consistency or performance. Maybe it helped the valves and guides a bit...
That being said, anyone who uses pump Premium gas, (whether you mix it or not), needs to keep this in mind: These current day gas pumps with a single hose for all 3 grades of fuel, you can bet the first gallon or so into your jug is gonna be regular gas, at least 90% of the time. Some simple math will tell ya that for a 5 gallon jug, and your preferred purchase of 93 octane, if only the first gallon is 87 octane, you end up with a net fuel octane in your jug of 91.8, and if your premium is only 92 octane, you end up with 91 in your can.
I don't know the actual volume it takes to clear out the previous customers' fuel from those long hoses, (plus whatever is inside the pump), but if it happens to be 2 gallons, then you are really only getting 5 gallons of 90.6 octane (if Premium is 93), and if your pump premium is 92, you wind up getting some 90 octane results in your jug.
If you are filling a little 1 gallon can for your lawn mower, scooter, weed whacker, etc - Then you are paying for premium, and getting regular.
The solution is to stick the nozzle in your vehicle, and pump 2 gallons into that tank, (consider it a little treat for your daily/tow vehicle), THEN fill your fuel jug(s), and you know you will get whatever is in the premium tank, (hopefully what the pump is labeled as).
Just don't use this trick if your tow vehicle is a diesel...