Fuel Questions

[Lquad71]

Just some questions about what types of fuel does what?

Whats are the differences between leaded and unleaded? I think leaded has more lubricating properties but not sure.

What is better to run for racing between oxygenated and non-oxygenated fuels.

What do certain values of gravity mean?
Is .765 be better than .71? Or vice versa? and why? what does the gravity do to how it runs?
Thanks in advance

[wilkin250r]

Leaded fuel has an additive in it called Tetraethyl lead. Yes, it lubricates better, but that's not the goal.

Tetraethyl lead is a fantastic additive for increasing the octane rating of fuel, it requires much lower concentrations compared to many other octane boosters (so you're not diluting the gasoline), and it's really stable. During the development of leaded gasoline, the other popular alternative for octane boosting was ethyl alcohol, which required much higher concentrations, and the alcohol tended to absorb moisture over time. The lubricating properties of the lead was just a bonus.

Problem is, it's fairly toxic (of course, not too many byproducts of an internal combustion engine are "good" for you). And it will ruin your modern catalytic converter and 02 sensors pretty quickly if run in a modern-day automobile with all the emissions equipment on it.

[wilkin250r]

And I'm not 100% certain on specific gravity, but I don't think it's a matter of a target number, like one specific gravity is better than another, but rather it's just provided as a means for comparison.

Specific gravity is a ratio of the density of the fuel as related to the density of water. That doesn't mean much, except that a smaller specific gravity is a "lighter" fuel, it has less density and therefore less weight.

This can be important for jetting, because the amount of fuel you draw in through your carburetor will depend on the weight and density of the fuel, along with various other factors. If you change to a "heavier" or a "lighter" fuel (as indicated by a change in specific gravity), you'll have a corresponding jetting change to compensate.