Vegetable oil.
Don't know if this has been posted yet, probably has.
Don't buy Diesel, it costs lots. Instead, find places that use a lot of cooking oil, and ask if you can have it.
Then proceed to filter it, add 10% thinner (I use petrol) and presto!
I run a 2.8 Turbo Diesel Iveco Daily on the stuff, and it's flipping great.
Slightly less economical, but hey, it's free.
Test it mixed in with your Diesel first, in small doses.

Also.. Technically, you're supposed to have paperwork to show where it's all going, and that it's not just being dumped.
(Sir Clitherington Smythe offers him yourself., Tue 15 Nov 2011, 3:39, 9 replies)

"Slightly less economical, but hey, it's free."
Hmmm, let me ponder that for a moment.
( Ghoti Fingers, Tue 15 Nov 2011, 7:00, closed)

meaning less mpg
( enoughblueskyforsailorstrousers, Tue 15 Nov 2011, 8:02, closed)

"Economical" in the sense of how much you use. In other words, running on veg oil takes a little more fuel in terms of volume, but it doesn't cost anything.
(gordonjcp, Tue 15 Nov 2011, 8:02, closed)

Thanks for the clear up!
That is indeed what I meant. It uses more Veggie oil than Diesel, but it's cost more than makes up for it.. I don't advise running it on straight oil, it gets pretty juddery.
(Sir Clitherington Smythe offers him yourself., Tue 15 Nov 2011, 14:51, closed)

Beware the fatties chasing you cause your
car smells like a fish & chip shop!
(Misery McUglywife an attention seeking sociopathic fuckstain., Tue 15 Nov 2011, 8:15, closed)

Indeed!
Sometimes, if it misfires, I imagine a sausage being launched out of the exhaust. This makes me chuckle!
(Sir Clitherington Smythe offers him yourself., Tue 15 Nov 2011, 15:05, closed)

You can use up to 2000 litres
before customs & excise start taking notice. But then, 2000 litres is quite a lot. I was doing maybe 12000 miles in a 2.0l petrol Renault and using nowhere near that, so on a diesel engine it would be even less.
( sandettie light vessel automatic New Twitter - @bollocksreally, Tue 15 Nov 2011, 8:48, closed)

I'm told...
...you need the right kind of fuel pump in your car, or you'll be in trouble.
( Scaryduck LIKES EGG, Tue 15 Nov 2011, 13:44, closed)

This is
Possible, but tried this on two vans now and never had a problem.
I think maybe a car would be less keen to run on it, and a mate of mine had an old Bedford that did NOT like it at all. Only try it if you have something that didn't cost you the Earth, I suppose.
Got the Iveco for £400, and I work in a super busy kitchen, so the fuel has been free all summer. The money saved is just amazing.
(Sir Clitherington Smythe offers him yourself., Tue 15 Nov 2011, 14:56, closed)