A friend of mine told me that his father mixes a little diesel into his gas tank from time to time to clean the internals of his motor. Says he's always done it and his cars/trucks have lasted a long time.

Is there any truth to this?

 

I've heard that a few times to. I've never added a lil to the fuel though. I have filled an engine with diesel and let it sit for a few days then drained, (NOT suggesting). Cleaned up the motor all right, smoked for days and days once I finally got it cranked again.

I don't know how adding it to the fuel would clean the internals of the motor, maybe the fuel lines. But as soon as it goes into the cylinders it'll burn off. The diesel would never touch the rocker arms and valves and all that.

 

I've heard of using diesel engine oil (at least a mixture with regular engine oil) to clean out the internals. Supposedly, the diesel engine oil has stronger detergents and such since the diesel engines tend to be dirtier. I've never tried it, but would be worth a try I guess. Sounds about right to me since the oil in diesels never stays clean. The oil almost always looks dirty after some miles (not a lot but a few). The diesel in the gas probably helps keep the fuel lines, fuel pump, injectors, intake, and intake valves clean. To clean out my truck I use Sea Foam (through the intake and inside of the oil). If you use Sea Foam, read the instructions since you cannot run your oil that much longer after putting in Sea Foam.

 

this sounds like a bad idea to me. like nauticstar87 it would make it smoke. might clog up some valves too

 

I wouldn't try it with today's fuel injected system there are plenty of additives you can buy to do the same thing. Diesel is a fuel oil and not as refined as gas.

 

This is not recommended, I woudn't mix a small amount of diesel in gas because it can clog up the fuel filter.
Also, watch this - What Happens When You Put Diesel in Gasoline?

 

Why do this. They have fuel injection cleaning systems designed for this. On modern engines with direct injection you need a way to clean the valves and this requires a injector placed in the induction system.