I'm really considering adding some 104 unleaded into my turbo car for added protection against detotation and knock. But I'm worried about mixing 93 octane pump gas with sunoco 104 unleaded gas (unless I should mix a leaded gas, if you think its better). I'm worried because the specific gravity of both gases is different and I'm not sure if the gases will mix appropriately in the gas tank and into the combustion process. Can anyone steer me in the right direction? I was considering just doing a simple 50/50 mix of pump and race gas. I'm not sure if this would do more harm to my motor than good, however.

Any thoughts?

 

Nothing wrong with mixing fuels. I've done it before when going from a track day to daily driving.

High octane unleaded fuel is expensive. Why not run leaded fuel? Lead is bad for cats and 02 sensors but most FI vehicles don't have cats. 02 sensors will get a little less responsive over time but its isn't anything worth freaking out about. It takes a couple years of leaded track days to get to them.

 

Just make sure you tune your car with those fuel(s) also..

 

I've drove my car on a pump gas tune with a little leftover race gas before. I wouldn't do it the other way around but having higher octane fuel while running lower boost won't hurt anything.

 

My tuner recommended adding a little 110 or 112 from the track pump for race days and said it would not need retune its just a little added protection against detonation... I think you should be all right

 

Unless you have a stock K20 fuel setup, your fuel pump runs at full speed. At idle, 99% of it is returned to the tank, so it gets mixed quite a bit.

The other thing about gasoline is that it's not one single molecule. There are several types of hydrocarbons in it, from iso-octane to heptane. There are also additives to help stabilize the fuel, and oils to help lube the pump, injectors, seals, etc.

As long as you're not adding WATER or let it stand for a year, you'll be fine.


The question I have...why would you get it tuned on 93 but not trust it? Anyone tuning a motor that will run for more than a few 1/4 mile passes should not be on the bleeding edge of the timing curve. Hell I just saw a motor get tuned to ~360whp on 91 octane. What kinda motor do you have that you're so worried about knock?

 

ive mixed C16 with 94 octane pump gas and had great success.