On saturday this weekend a guy came into the shop with his truck on the tow truck. He had accidentally put gasoline in his 05 GMC Duramax and luckily realized this when he went to put the cap back on the tank. So he had it towed to our shop. He said he had put 22 gallons of gas in the tank. After hearing this I asked if I could pump the fuel out of his tank and into my 91 250 with the 460, he needed a way to get rid of the fuel so he did not care. I knew the diesel would be pretty diluted with regular gas. So I basically got one free fill of my rear fuel tank.

So today I leave for school wondering how the 460 will run with a little diesel mixed in the gas. Well she runs good but will ping moderately if I give her to much throttle, and I can probably guess that it is because when the Gasoline ignites and gets to a certain temperature the slightly remaining diesel then suddenly ignites and causes pinging, so if around town I just let off the throttle slightly and it goes away, and for going over the grade I switch to the front and there is no pinging at all.

I don't think I am doing any damage at all because when I run 87 right out of the pump the ole girl will also ping slightly under a pretty good load (75MPH over a 6% grade). And I Definately don't floor it while I am running on this slightly mixed gas because I do not want burn a hole in the piston.

So do you guys think this is a bad idea or okay because as soon as she makes the slightest noise I let off the gas?

Also i will say that the lucas fuel additive is good stuff because like I said the 460 will ping slightly under a moderate load with 87 but when i mix in the lucas and go over the grade the occasional ping is gone. I don't know if the lucas acts like a retarder to the gas but any way it works.

 

Sounds like it should be ok. When the tank is half empty, I would probably add some fresh gas to the rear tank to further dilute the "free stuff".

 

if you are getting some light pinging under hard load with 87 you should either try mixing som 93 with it or dial back your timing just a bit. even .5 degrees will help that. My mustang at 12 degrees of timing will not run on anything but the 93. I have to dial it back to 9 to get it to run on 87.

 

on my old tractors ill put a lil desiel in with the gas every time i fill them up. i believe it helps cushion the valves a lil cuzz the of the unleaded gas,they've ben runin that way for years no problems