Hi, a friend recently told me that he put a little diesel in his ranger when he filled up the other day. He said that he heard this caused your truck to get better gas mileage… im just wondering if it is true.
No.
As long as the amount is very small (a few oz) it is not likely to hurt, but it is not really going to help a properly functioning gasoline car.
Mixing diesel with gas will lower you fuel’s octane rating. The octane rating of diesel is less than zero. Cetane rating is just the opposite of octane rating. It measures how easily a fuel ignites rather than how well it resists ignition. Diesel knock comes from delayed ignition after the fuel is injected.
Want better gas mileage? Quit accelerating towards red lights.
For what it’s worth, diesel fuel does have a higher energy content per gallon than gasoline. I think it’s around 140,000 BTU per gallon verses about 119,000 BTU per gallon for gasoline. So blending diesel with your gas is just the opposite of blending ethanol with your gas. If the engine doesn’t detonate, it is concievable that your mpg could increase slightly. You might have to use premium gas to offset the octane lowering effect of adding diesel. I doubt that you will save any money.
That was done when diesel used to be a lot cheaper which it isn’t today. People only did it on real junkers. It could be added up to the point the engine knocked real bad. I’d say don’t tell him and lets see how long it takes to gum up the plugs and valves.