As far as using two stroke in fuel goes there are varied views on it benefits but this article below sort of puts it into perspective.
Adding 2 Stroke Oil to Diesel
A liter per fill of good old cooking oil is more than adequate and a fraction of the price. As far as more MPG goes its all down to the right foot, the manufacturers mpg figures can be beaten and some times doubled with careful use of the right foot.
Bob
Article below.
Contributor: Stuart Bladon
After 26 years on Autocar magazine, where he was deputy editor, Stuart became a freelance writer in 1981. His interest in economy driving dates from a first attempt at the Mobil Economy Run in 1961 with a Rover 3-litre, and in July 1984 he achieved an entry in The Guinness Book of Records by driving an Audi 100 turbo diesel from Land's End to John o' Groats and back as far as Falkirk without refuelling. Total distance was 1,150.3 miles, at 59.27 mpg. When the record was broken by a Toyota Land Cruiser fitted with an extra fuel tank, he tried again with the later Audi 100 turbo diesel, and retrieved the record by going from John o' Groats to Land's End, and back to Scotland, all on one tankful, 1,338.1 miles at 75.94 mpg. The tank finally ran dry on A74 at the then-little known town of Lockerbie. He also established the world record distance for production car economy, covering 112.01 miles on a single gallon of diesel fuel with a Citroën AX 14DTR. But he claims that his most successful economy drive with a petrol car was in October 1997 with a Mitsubishi Carisma GDI. Flagged away from Earls Court on the opening day of the Motor Show, the Carisma traversed France without refuelling, and then went right across Spain and over the ferry to Tangier. Total length of the London-Morocco journey was 1,658.4 miles, at an average fuel consumption of 65.06 mpg. Total fuel used was 25.49 gallons - less than two tankfuls. Stuart's
experience as a Road Tester began soon after joining Autocar 46 years ago, and included testing a Lamborghini Miura at 172 mph. He drives about 80 different cars a year, averaging a total of 28-30,000 miles, and has been Road Tester for Wessex Wheels from the first issue of the magazine, which has now grown into the web publication Gear Wheels at Welcome to Gear Wheels and Wessex Wheels Motoring Magazine