I ran into a gentleman at a recent Jaguar show and he told me that he uses aviation gas in his series lll. He explained that it contains lead and doesn't deteriorate and varnish nearly as fast. He also indicated that the car performers much better as well. Just curious if any one else can shed any information on this subject?

Submitted by bonnettoboot@e… on Thu, 12/05/2013 - 23:05

There is a downside to Avgas, it certainly allows for more power but it can also burn out valves. ( personal experience). And don't get mixed up with Avtur!

Submitted by alan.barc@veri… on Thu, 12/05/2013 - 16:19

You're right on George. It's just like copper roofs etc that turn green over time

Submitted by SE98-32482CJ on Thu, 12/05/2013 - 14:21

The "Green Stuff" is /was the brass needles and a few other bits reacting to the water and air. I think the proper name is verdigris (SP?)

Submitted by tidewaterinsp@… on Thu, 12/05/2013 - 14:17

The problem with the current gas we buy at the pumps is the ethanol. It's junk. Ethanol has about 80K BTU/gallon. Real gas has around 120K BTU/gallon. The ethanol also has water in it. That may be why when I used to lift the pistons on the SUs I would see green stuff on the mixture needles. I switched to Avgas and found that my 62 E type runs a lot better and I don't have green stuff in my carbs anymore. If anybody knows what the green stuff was let me know.

Submitted by NC98-56048 on Mon, 10/07/2013 - 23:51

Howard; Years ago when I flew and when my dad's Jag (now mine) was near the airport (small town rural NE) we would drive up to the gas pump and fill the tank of the Jag. Ran great and we always thought it performed better but that may have been wishful thinking.
The problem with this process is that it cheats the State and Feds out of 'gas tax dollars'. I know of no one that has been stopped for this. Farmers and ranchers will get stopped and the fuel in their road vehicles better not be farm fuel or the will pay a significant fine.

Submitted by SE12-44804 on Mon, 10/07/2013 - 12:48

My two cents:
Sunoco sells 100 octane (with 10% ethanol) that can be pumped directly to your car.
They also sell 110 octane without ethanol, but you can not pump it directly into your car.
You may have to check around to find a station that carries these two grades.
I use the 100 octane in my 68 E-Type.

If there is a race track anywhere nearby, check there also.

Submitted by joshbartlett@r… on Mon, 10/07/2013 - 12:23

Higher octane fuel, like avgas, will give you more power because you can then advance the timing further and can run higher compression ratios. I'm not sure about resetting carb. mixtures....

Putting Avgas in a modern car that is set up for 89 octane will not give any difference in performance. However, many of us use it because it does not (as yet) contain any alcohol and does contain a little lead. Perfectly acceptable and legal (in most states) for cars without catalytic converters, not legal for cars with catalytic converters; it will hurt them.

Avgas is also good to prevent the damage done to small engines like chainsaws, leafblowers, etc. by gasoline/alcohol mix required to be sold in many states.
Josh Bartlett
1997 XK-8
1969 E-Type
1937 Packard 115c

Submitted by hilstonsmg@aol.com on Mon, 10/07/2013 - 10:11

Howard, Back in the 50's while in the Air Force, we used 115/145 Avgas in our cars quite a lot. Often mixing it with what was in the tank and with no problems. Got a big bost in power and it was great for street racing but not legal on drag strips. I don't remember any down side except for the fear of getting caught stealing it from the C-124's that we were working on, it was a job perk that was usually not inforced. That was at Dover AFB and we needed the fuel to get away from that dull area. I don't see a problem using it in your Jag other than cost or resetting your carb mixture maybe, all 4 of them. Let us know how it goes, I'll stick to premum at the pump at my local station in my S-1.
Good luck, Don Hilston