What is the most fuel you have put in your tank?

Dave,

I think only around 14 gal, which clearly is not pushing capacity limits. I have this fear of bottom of tank sediments getting out of the tanks, mixed with my other fear of the notorious flying 1/4ths to 3/4ths gas gauge, making me top her off compulsively. If the gauge swings below half at any point in a ride, I fill up.

 

Dave, I just ran my T down to "E" and then some. I squeezed 15.2 in 'er at fill up. My literature shows 22.7 as capacity, but with the "two stage" configuration of the tank I dont think I can fill both sides effectively.

 

I think 16 or 17 gallons was my top. When the low fuel light comes on solid I fill up. Usually before. I didn't think the tanks were that large. Very interesting.

 

we should put a can of Dry Gas in our tank?

What do you think?

I also have heard of a Stabil product that treats ethanol gas for older cars....

- Ron

 

Dave:

OK, I've been obsessing about fuel systems lately, so here are a few thoughts:

Considering that your car was significantly low on fuel, it's possible something in the tank got loose and partially obstructed the fuel intake filter located in the tank. Maybe the subsequent fill-up stirred things up enough that the piece of whatever-it-was has ended up somewhere else. It might still be there, maybe it floats. I know this is not comforting, but I've had problems with stuff in fuel tanks causing this sort of problem. Usually it's something like rust or something that got dropped into the tank (e.g. the foil used to seal drygas bottles can end up in there.) Let's just say that I didn't really enjoy the time spent fixing this sort of thing on any of those occasions. I wouldn't run it low just in case there's something still floating around in there.

This may actually be a better scenario than a problem brought about by using fuel containing alcohol... read on...

Ron mentioned drygas and Stabil -- Here's what I've found:

Alcohol in fuels is both an octane booster and a strong solvent. There are a few issues that stem from this:

Running a fuel like E10 will remove significant amount of deposits that might have been harmlessly adhered to internal surfaces in the good ol' days. This may initially clog filters or obstruct small passages, but after replacing/cleaning that stuff you should be ok.

As many threads on here have pointed out, older fuel system components (particularly hoses) that were not designed to be alcohol-resistant can fail catastrophically; hence Dave Helms' fuel hoses which are rigorously researched and specified to a very high standard. It would seem from the many posts that this is a real problem that all of us will be required to address, unless our cars are fairly recent. And the alcohol's solvent properties would seem to be a good way to get pieces of old hose in your fuel distributor, injector lines, and injectors. I'm in denial for the time being until I re-do the hoses

There is also the concern that since ethyl alcohol and water are completely miscible, the water-bearing alcohol can corrode metals. Even worse, "phase separation" can occur. In this latter case the alcohol-water solution settles to the bottom of the tank. There are then two problems: The alcohol-water solution is not combustible, and the remaining gasoline now has a reduced octane rating ('cos the alcohol is no longer mixed with it.) I've read gasoline manufacturer's literature which suggests this is very unlikely, but I've also drained water/alcohol out of my lawn mower's fuel tank after it separated. Advice I've heard is if this happens, throw out all of the fuel.

Dry gas is just more alcohol, so this may not be a sensible thing to add if there is already a lot of alcohol in the fuel.

With regard to Stabil, I have an anecdotal remark to share: A friend who is both a marvelously skilled mechanic as well as an Aprilia and Vespa dealer suggests using "Marine Stabil" as opposed to the regular stuff, and using it religiously. Every spring his shop gets a lot of service business for bikes and scooters that have fuel system problems, and these are the units that were simply stored without any fuel preservative. (We are in New England, a cold climate). His recommendation if you're going to store a vehicle for a long time, to remove all of the fuel and prepare the engine for storage... but I can't conceive of this for my Ferrari, so I just use lots of Stabil and try to run it regularly.

Have a look at Shell UK's response to a discussion of this on the Triple-M MG Register Forums (about halfway down):

http://www.triple-mregister.org/forums/topic.asp?TOPIC_ID=4260

I now use Marine Stabil in all of my vehicles. Here in Connecticut, E10 is pretty much a requirement, so finding alcohol-free fuel here seems challenging... even the boatyards seem to be selling E10 around here these days.

Since alcohol is also an oxygenator, it can mess up the stoichiometric air/fuel ratio. The air cooled guys apparently have it worse: An old 911 running hot because of the resultant lean mixture can really have issues according to those guys. Modern cars which adjust mixture according to an O2 sensor can at least compensate, and water coolers can dissipate the excess heat caused by lean running.

I can cite references on any of the things I've said here, if anyone wants to research this more. And I could have misspoke on something, but I think this is substantially correct.

I'm still trying to research winter versus summer fuel blends with regard to alcohol content, there's a lot of chatter about it on the net but I haven't seen anything other than opinions so far. And we all know the value of opinions.

And in spite of these risks, My friend the motorcycle dealer suggests E10 will probably result in a very clean fuel system in the long term once these issues are addressed.

By the way, I usually put 14-16 gallons in per fill-up.

Charles

 

Dave:

I agree with your analysis: a common fault with two separate fuel delivery systems suggests that it was a problem with the fuel. It could well be phase separation, as a condensing atmosphere in the tanks would lead to water accumulation, especially if the fuel system was vented. (Is the carbon canister intact? Maybe a vapor line is vented to atmosphere?) Also, you might have had a fill-up at some point with a bad mixture or gas containing water. (Here in CT we had a number of stations which took delivery of gasoline containing brine a few weeks ago -- killed a lot of cars in two days. The problem was traced to a specific tank at a terminal near New Haven, so this sort of thing can happen.)

Scary stuff... I hope this is your last encounter with this issue.

Charles