Formula52

Hi all,

Was listening to the C7 maintenance seminar on Saturday at Carlisle. The engineer giving it said to let the gas run down to 1/8 a tank before filling. Something about some chemical in the gas that is not good for the gas sending units to stay submerged in gas all the time. It messes up the gas gauge. He said they got a call from Spring Mountain asking what was going on. They constantly refilled after each session. That was found to be the answer.

He also stated that the car if stored for more than 90 days, should be at 1/8 a tank of gas. Not sure I like that idea. Stored last year with full tank with no problems.

What do you guys think?

Steve

Foosh

I've never heard of a issue similar to this before.

A car stored w/ a nearly empty tank can also develop a lot of condensation in the tank. The conventional wisdom has always been to store a vehicle w/ a full tank to avoid this.

7thgeneration

Letting the gas get too low can burn up the pump as well. Did that a few times on my Cavalier and had to replace it. So sounds to me like a no win situation to me.

Flame Red

- that's a new one. The old consensus was to keep it full so that the gas gauge would not get "etched" (if that is the right term) and need replacing ($$$$$$$$$$$$$$$$$$$$). Better if the sensor gauge was constantly submerged in gas - or so was the general wisdom.

Greg00Coupe

Sounds odd to me but you heard it from the horses mouth.

Better solution..........trade before the warranty is up!

DickieDoo

Yes, fuel is supposed to be used as a coolant for the fuel pump, hence never let it get that low...
However on the C7, there are two tanks and pumps that equalize the tanks. I believe that they are constantly working. From what i've heard, there have never been very many problems with fuel pumps.
It may be good practice to let it get low once in a while.

Rebel Yell

Ummm that's different. Or was he saying this because the sending unit in these cars were made by little Mae Ling, and she was on her 13th hour of a 15 hour day?

JoesC5

Odd that the "chemical" in the gas doesn't ruin all the tens of millions of gas sending units in other brands of cars. Maybe it's not the "chemical" in the gas that's the problem, but the gas sending unit's engineering.

Steve_R

I've never heard of such a thing in all the years I've owned a lot of different cars.

Formula52

I fully agree...

Bill Dearborn

It does. It is sulfur and the refineries are supposed to reduce it as much as possible but sometimes a bunch of bad gas gets delivered to an area. It will hit all gas stations since they all buy from the same refinery. You will notice a sudden surge of complaints in the newspaper where a bunch of people start complaining about their gas gauges going bad.

An 1/8 of a tank of gas isn't going to kill the fuel pump since there is several gallons still in the tank. If you run it really low into the so called fuel reserve then you might have an issue due to there not being enough gas. However, when you get that low there isn't much fuel pump operating time left anyway and most people turn off the ignition when they run out of gas.

Bill

JK 23112

With ethanol-laced gasoline being sold in so many places, I would be worried about it a bit during colder weather. Ethanol has an affinity to attract moisture - which is not good for automotive components. When you let your tank get really low (ethanol in gas or not), there is more chance for condensation in there.

Most new cars are designed for E-10, but it can cause trouble in older cars.

JoesC5

The C5 was notorious for the sender problem and my C5 had the senders replaced. None of my other cars had the senders malfunction and they all were gassed at the same gas stations.

It was discussed on this forum many, many times.

When my C5 was having problems(over a couple of years) I never heard or read about all those other cars in my town having sender problems that you think also occurred. The only car I added Techron to was my C5 back then to keep the gas gauge from going stupid on the car. My other cars never needed Techron.

rcooper

I have always let my tank get to 1/8 or less before filling. I have never had a problem with any of the sending units or pumps. 2- C5's, 1-C6 and my C7, over 200,000 miles with out an issue.
Maybe they are really knowledgeable or stumbled on it, but it seems that I am just as smart...LOL.

Skid Row Joe

Ditto.

Sounds like there might be some re-engineering in order, if the part (s) cannot withstand extended time in fuel immersion?

As to keeping a full tank? I'm guilty of not keeping full tanks of diesel fuel in my RV and diesel car's tanks. I use Power Service quite often in the Winter in my diesels. My small gas engines for lawn maintenance, use Stabil in their fuel year around.

UncleFodder

My C5 took a steady diet of Techron to ensure the sending unit (and hence the gas gauge) stayed functional.

Vetteman Jack

I haven't either. I think I'll continue to fill my car up when it gets down to no lower than 1/4 tank and when storing the car will do so with the tank full.

Corgidog1

The advice you received kind of goes against what is common practices, however what I plan on doing is running my tank down to 1/8th every once in awhile and keeping a full tank when the car is not used for long periods of time due to bad winter weather.

cv67

gotta love some of the "experts", oughta be working for GM.


OP that is a crock what you were told