Adding Diesel to gasoline

[lindsayjim]

Straight gasoline = 15 mpg, 30% diesel blend = 18 mpg

Here at present low octane gasoline is $3.25/gal and Winter diesel is $3.55/gal

$3.25/15 miles = $0.2167 / mile

(3.25x.7) + (3.55x.3) = 2.275 + 1.06= $3.335 / gal blend

$3.335/18 miles = $0.1853 / mile

A saving of $31.40 per thousand miles in fuel cost.

I am experiencing no smoking or misfire. I discount all fears of filter clogging, injector clogging or valve stem depositions. If I've misjudged the fuel system seal compatibility I'll pay a hefty penalty. If there were misfiring then I'd be concerned about the cat., but absent the misfire I expect it to have a normal life.

[Christ]

I presume you've tested to a satisfactory extent and found that under your conditions, 30% is the most effective blend?

Have you noticed a change in engine running temps? I found that with diesel, my engines tend to "feel" a little bit hotter, but I haven't actually recorded temps to find out, since ABA testing would require drain/fill cycles, and I don't have time/patience for that.

[MadisonMPG]

When I am making bio diesel I usually burn one or two car tires, helps keep the world in check.

[lindsayjim]

It's a bit tough to get accurate test data with so many uncontrolled variables in actual driving conditions. 50% was definitely too much as indicated by poor cold temperature starting and idle as well as slight misfire under load. There were small incremental increases in mileage in the 10-30% range. My metering is not perfect, but I use the scan guage to judge consumption, then first add 1/3 diesel, move to the regular pump and complete the fill-up. Close enough to 30% for my purposes. Whether it is actually ideal..... can't say with certainty, but close enough for practical purposes.

[lindsayjim]

Running temperatures are normal, riding on the thermostat at 190 whether straight gasoline or blended mix.

[pgfpro]

I deleted my last post I need to get some sleep.LOL

Anyway very informative. I just might have to try this on my company truck.

[The Atomic Ass]

Originally Posted by Christ

I've run straight diesel in a gas engine.

I don't suppose you have any data on the FE with straight diesel?

[tjts1]

Does adding diesel fuel to gasoline in any proportion increase or decrease the overall octane rating for the fuel?

[Christ]

Originally Posted by The Atomic Ass

I don't suppose you have any data on the FE with straight diesel?

I don't, unfortunately, and I haven't had to do it enough to really have gotten any reputable data to begin with. TBH, I've only ever owned two cars that could use a SG, and I'm driving one of them now... the other is my wife's.

When I used to put diesel in my cars, I was like 16-18, always running out of fuel, etc. Right now, I don't think I'd be quite as willing to do it, but I'm not really sure why... probably because I have a gas station next door, and I actually pay attention to my fuel gauge now.

I've read in older Briggs and Stratton manuals that you could convert most of their gas only engines to diesel... they say to expect a power loss of about 20-30%, and an economy increase (run time on a metered tank at X load) of up to 30%, if that helps at all. I've never converted one, or tested the theory with a small engine, though.

I'll tell you what, though... I can give you a single tank reading when I pull the van off the road... I'll put 5 gallons of diesel in 15 of gas, fill the tank, and drive it out, then refill with gasoline. Its not accurate, but you've seen my average, so it'll be kinda obvious if there's a big increase that something worked.

Originally Posted by tjts1

Does adding diesel fuel to gasoline in any proportion increase or decrease the overall octane rating for the fuel?

I dunno, actually... Diesel's knock rating is in Cetane, not Octane... I dunno how to measure Octane levels on my own, and don't have a test block to do it with, so I couldn't honestly say.

Cetane and Octane are "made up" numbers, which give you an idea of the chemical composition of the fuel... Cetane, at higher numbers, gives a higher chance of autoignition, which is desirable in those type engines.

Octane, on the other hand, measures the resistance to compression ignition, a completely different beast.

Cetane is an alkaline molecule that ignites under very low compression situations. It has a Cetane number of 100. The higher your oil fuel's cetane number, the lower compression is required to ignite it.



Read more: cetane number - Comparison to Octane Rating, Chemical Relavance, Measuring Cetane Number, See Also, External Links cetane number - Comparison to Octane Rating, Chemical Relavance, Measuring Cetane Number, See Also, External Links

[Frank Lee]

I'd imagine any gains from diesel fuel are from the higher Btu content.