Adding Diesel to gasoline - Fuel Economy, Hypermiling, EcoModding News and Forum

lindsayjim · 11-26-2009, 05:53 AM

I've been running a 2005 Chevrolet 6.0L fuel injected van on diesel:gasoline mix at a ratio of between 30:70 & 40:60 successfully. 50:50 was too high when the ambient temperatures were -15 deg. F., but the lower ratios have worked well. Cold starting is OK, although it is necessary to allow the engine to warm a couple minutes before driving away to avoid stalling. There is no apparent misfire and fuel economy is improved. My experience using a blend in this range has been an increase in miles per gallon of 10-20% over straight gasoline. If the improvement were due only to the difference in specific heat, then the increase should be only slightly over 10%.

underitall · 11-26-2009, 11:01 AM

Hmm.
That's quite interesting.
I'v always wondered why Diesel wouldn't work in a Petrol engine, but knowing that it can work to some degree, is quite good.
So, just say, you had a 100 litre tank, filled up 70 litres of Petrol, then would you just go ahead and put 30 litres of Diesel in, or is there some way in which you have to mix it up for best results?
Thanks,
Tom.

Piwoslaw · 11-26-2009, 04:26 PM

Petrol + Diesel : Why do two-stroke engines come to mind? Didn't two-stroke engined cars from the 1960's run on a diesel/gas mix? I've never heard of it working in a four banger.

Ryland · 11-26-2009, 09:18 PM

petrol diesel will clog your catolitic converter over time, this is due to the high sulfur content (50ppm in the US), I've run bio-diesel in my motorcycle at 10% without any issue at all, a very slight increase in mileage with a carburator but with fuel injection should be even better, at that 10% I had no decrease in power or top speed (it was on a 125cc Honda motorcycle) bio-diesel is sulfur free and acts not only as a fuel but as a top end lube, it's also a bio-fuel.

Cd · 11-26-2009, 10:15 PM

Did I read that right .... you can add biodiesel to gasoline and have it actually run in a gas engine ??

What's the catch ?

Christ · 11-26-2009, 11:53 PM

It gums up the exhaust valves, but not so much that you can't clean the engine once in awhile to keep it in check.

I've run straight diesel in a gas engine. You need gas to start it, but you can switch it over afterward. It requires some minor carb retuning sometimes, and FI ECU's don't really like it, but it can be done. I've never advocated doing it on a normal basis, though. I've done it in a pinch, where I had diesel fuel and no gasoline. If I knew I couldn't get anywhere without fueling up, I'd put the diesel fuel in the gas tank while I still had some gas enough to keep the engine running. Cold starting a gas engine on straight diesel isn't fun, and you should have 2 or 3 batteries and a can of ether on hand if you want to try it. It's a PITA.

Ryland · 11-27-2009, 10:35 AM

Quote:

Originally Posted by Cd

Did I read that right .... you can add biodiesel to gasoline and have it actually run in a gas engine ??

What's the catch ?

I tried as much as 50% bio-diesel and at that point I didn't have full power, the fuel acted like it wasn't burning fully, or maybe fast enough, it smoked alot and sputtered at high revs, 20% bio-diesel it ran pretty well, a little smoke and a little sputtering at the highest revs, with 10% I couldn't tell the difference between the 1:9 mix of gas and the 100% gas other then a very faint Chinese food smell in the exhaust, the power was the same all the way up to redline, my top speed on the 125cc motorcycle was the same, the o2 sensor that I installed in the exhaust looked just fine, the spark plug looked perfect, I did not take any mixed with gas to see if it separated out weird or anything.
my gas mileage didn't change a great deal after adjusting for the extra 10% fuel in my tank, but it didn't drop either.

Christ · 11-27-2009, 01:04 PM

So, if gasoline costs $3.00 a gallon, and BD can be made for $1.00 per gallon, and you can use 9:1 gas/BD, your fuel costs will be $2.80/gallon on average. It's the same as getting a few more MPG, right? And potentially cleaner.

Cd · 11-27-2009, 02:42 PM

Well if it causes more smoke, then apparently the emissions are worse.
Cost isn't even a consideration.

Christ · 11-27-2009, 02:47 PM

It doesn't always cause more smoke, though. If you mix too much in, it doesn't have time to burn fully. The more you mix in, the higher you have to advance the timing. There's a break even point, like with everything, and there there's a point of diminishing returns.

Spark ignited diesel isn't a new concept, it can be executed cleanly, but requires proper tuning, as with any modification.