Low Fuel Lamp: How many gallons left when light goes on?

Thanks, Aaron... You are, of course, numerically correct - I just felt slammed against that date.

Also: Len, thanks for filling out your signature. Now that I see you have a '97 like my own, I'd say that you have about 2.5 gallons when the low-fuel light comes on, which is right in the original zone...

Also, a 3.4" pulley is a little dangerous without any supporting mods, like the gutted lid, cooler stat, bigger downpipe, etc. Do you have a scan-tool? The mild mods in my Signature are enough for me to run a 3.5" pulley with 91 octane...

Eldo wrote:

I just want to point out that I agree about thicker oil for worn engines, but I can't see the theory of thicker oil (20W-50) being for higher revving engines... It's 20 weight when cold, and 50 weight when hot - not exactly something you want to have if you're gonna' zing high revs.
I ran 20/50 in my 400 inch Grand Am, but it was of course a torque monster, and also had 270,000 miles on it when I sold it.

I agree, thinner oil gives less drag and more HP, but when the engine is a big block Buick 455, there are other considerations. The BBB has one of the biggest crankshafts put into an engine. The crankshaft actually stabilizes the thin wall casting block. Those big 3.25" mains generate tremendous bearing speeds and tend to force oil out of the bearings at higher RPM. Add to that a front mounted oil pump that is subject to wear from improper maintenance, and it's no wonder the BBB has a reputation for weak oiling. Buick built the engine with tight bearing clearances for a reason. If the clearances are too big, there is a big drop off of oil pressure from the front to rear of the block, and the result is usually smoked #7 and #8 rod bearings. Lot's of guys who are new to Buicks have their engines built by shops that aren't familiar with building Buicks, so they build it like a Chevy, and that is what leads to insufficient oil pressure and short engine life. With most engines, 10 psi/1000 RPM is plenty of oil pressure, but with the BBB, you need 11-12 psi/1000 RPM. An oil pressure gauge is mandatory with a Buick. If you want to rev it to 5500 RPM, you want to see 65-70 psi at those engine speeds. Sometimes thicker oil is the only way to get that pressure. It certainly isn't the way you want it though. Attention to bearing clearances inside the engine, and inside the oil pump, and a BBB will run forever with 10W/30 up to and sometimes above 6000 RPM.

I wish I'd known about the zinc-phosphate issue when I last changed the oil in the Wildcat... though the oil I had on the shelf might have still been pre-SM. I think I'll still buy a bottle that ZDDPlus.

While Googling around, I found this:

Valvoline offers two solutions to the zinc issue:
1. Valvoline VR1: Contains 75% higher zinc than SM motor oil with a balanced additive package designed to work in both racing and street-legal applications. This product will protect older style push-rod and flat tappet engines. Valvoline provides this product in both multi and mono viscosity grades: 20w50, straight 50, 10w30, straight 30, straight 40, and straight 60.
2. Longer-Lasting Zinc/Phosphorus: Valvoline uses an advanced zinc/phosphorus additive that keeps higher levels of phosphorus in the motor oil where it protects the engine instead of poisoning the catalytic converter. Valvoline is the only brand offering this unique additive across its entire line of passenger car motor oils including SynPower -- the only synthetic offering this additive.

Have we finally gotten to the point of feeding our engines vitamin & mineral supplements for better health?

It's interesting stuff, please continue!

AA wrote:

Have we finally gotten to the point of feeding our engines vitamin & mineral supplements for better health?

It's interesting stuff, please continue!

Aaron,
Only flat tappet cams. Our Rivs and modern engines have roller cams.

Eldo wrote:

I wish I'd known about the zinc-phosphate issue when I last changed the oil in the Wildcat... though the oil I had on the shelf might have still been pre-SM. I think I'll still buy a bottle that ZDDPlus.

While Googling around, I found this:

Valvoline offers two solutions to the zinc issue:
1. Valvoline VR1: Contains 75% higher zinc than SM motor oil with a balanced additive package designed to work in both racing and street-legal applications. This product will protect older style push-rod and flat tappet engines. Valvoline provides this product in both multi and mono viscosity grades: 20w50, straight 50, 10w30, straight 30, straight 40, and straight 60.
2. Longer-Lasting Zinc/Phosphorus: Valvoline uses an advanced zinc/phosphorus additive that keeps higher levels of phosphorus in the motor oil where it protects the engine instead of poisoning the catalytic converter. Valvoline is the only brand offering this unique additive across its entire line of passenger car motor oils including SynPower -- the only synthetic offering this additive.

Excellent find. I'm glad there's an oil company addressing this issue directly. I still have several flat-tappet engines to maintain. No catalytic converters on either, so I've been using ZDDPlus in the oil. It's nice to hear about an oil that has what is needed.

I quickly parsed the owner's manual but couldn't find anything about this.

What do we have left when this light comes on, 3-4 gallons? Figure that gives us about 80-100 mile range if absolutely necessary?

Rick:

I don't know for sure, but I can tell you from experience, it aint much...at least not in mine. Perhaps 30-40 miles and that's about it.

Eek!

Let's see if this barge makes it home then. I have about a 55 mile commute this evening and the gauge is sitting on a little more than an 1/8 of a tank. Past experiences seem to dictate that the light will come on pretty soon.

Interesting thing to note is that I've filled up the tank after the light comes on and only gotten to about 15.5 gallons. I believe the full capacity of the tank is supposed to be 19, right?

People might wonder why I'm bothering to chance this. One is that I'm curious. I never let my tanks go much past a quarter so this will be interesting. Two is that the gas by my job and places on the way home is priced absurdly high.

All I can say is, take it easy. I think you're right about the 19 gallons. It may just be a quirk to my particular car.

I'm in the same boat as Dave, once the light goes on I must find a gas station right away. The wifey ran out of gas twice because s she thought she could "make it".. Come to find out she couldn't..

my experience is that the GM low level indicator light is not reliable.Mine will come on and 5 miles later Im stranded. Ive heard this from other GM owners.

Did you make it home? (I think yes)

the 96's had a 19.6 gallon tank. i have about 3 gallons left when the light comes on. (about 30 miles lol)
The 97+ rivsd had a slightly smaller gas tank but i dont recall the exact amount. 17.8 sounds right though.

I made it home fine. Thanks guys.

Light came on about 15 minutes before I hit the gas station (about 40 minutes into trip). Car only took 14 gallons? Seems odd. Wonder how conservative my sender is. I guess better that than the other way around.

You've got that right... Mine has run out of gas twice! no light! until the car was dead on the side of the road! one time for my wife it said 1/8 then once for me it said 1/4 tank. and yes on that 19 gal. atleast on my 95"

Are you guys doing this just to see what your reserve is, or do you routinely run that low on gas? Running the tank that low really heats up the fuel pump and shortens it's life.

You are sooo right, Larry.

I learned my lesson only because my Riv had less than an 1/8 of a tank when I bought it. Now, I always keep it at least 1/2 full. With today's rising gas prices, that's not a bad idea regardless, IMO.

I know it's generally said to be a bad idea to run low tanks for the reasons you gave, but to be fair to the engineers who created this specific pump, which is known to be a good one - they might have thought about this issue from the beginning. Just saying, I have always let my tank go near empty, almost every single tank (light on) before filling up. I did this on a weekly basis for over 220k miles before the pump began to fail. If I can get that many miles out of the OEM pump, considering my "reckless behavior", I really wonder how dangerous this habit really is. Could the pump use such a design that it still manages to stay cool enough, even when the tank is very low?

AA says: "I really wonder how dangerous this habit really is."

I don't know how "dangerous" it is, but it can be mighty inconvenient if you run out of gas... LOL !!!

What I noticed, and this may be an incorrect observation, is that the pump (or sender unit) seems to be located in the front of the Riv's tank. Whereas the Regal's is in the rear. My reasoning for this is that the gas gauge goes up in the Riv when on a decline and down on an incline. The reverse can be said for the Regal. This difference also may be explained by the shape of the tanks but I'm leaning towards location of sender unit.

With that, could it be bad to climb a hill or two when the tank is running close to low? It's an interesting theory if the pump isn't submerged and ends up crapping out because it runs too hot.

Interesting theories, but we are also making lots of assumptions. For example, the pump being submerged enough or too little might cause the gauge level to be affected, but does it affect the pump's cooling? I noticed when I removed my sending unit the pump is encased in a plastic reservoir. This reservoir fills with fuel at the tank's level, and would think the walls of the sending unit act as a baffle to keep the level of fuel more constant near the pump, accounting for brief periods where the fuel level changes. This is just another assumption, but we know the baffle is there for a reason. That is my take on it. The engineers were certainly familiar with the changing fuel levels in tanks, and the fact many drivers do let their tanks run low on occasion.

Another thing we may not be considering: what is the ideal temperature for the pump to operate? It might be assumed the hotter the pump gets, the shorter its life, but what we don't know is how hot is too hot, and if a low fuel situation actually allows this condition. The pump engineers may have considered a high operating temperature, and knowing the conditions, configured the pump to run hot without failure. Another assumption, but makes sense, imo.

Regarding the idea that the fuel pump failure is influenced by low fuel level, or climbing a hill - well, I just think the Riviera is a better car than that, and in my experience has proven to be such. As many fuel pump replacements that are reported here, most are high mile cars. I haven't heard of any sudden failures where low fuel or driving behavior has been labeled the cause. They just kind of go out at a certain age, sometimes taking a period of weeks or months to finally quit. To me, that's an ideal failure situation, giving some warning before failing completely.

I am still running the OEM fuel pump at 186k miles. ALL of which has been in sunny hot florida (87° right now :roll: )
I demand a lot out of my pump and thus far it still delivers enough fuel to keep up with 14 psi and 42.5lb injectors.
I also have gotten in the habit of driving until low on gas (didnt used to).

I really dont like being in the habit of waiting until the light is on but at the same time ive never stalled the car due to no gas.

I would say there is more of a chance that bad/dirty fuel over the course of 100k miles kills the pumps before low fuel level does.

That being said i have heard stories about people with failing pumps letting them sit and "cool off" or filling the tank with cool gas to keep the car going until the pump is replaced.

Hard to say. I'm pretty sure that an uncovered pump will run at a higher temperature than one surrounded at least partially with cool gasoline. Who knows Aaron, maybe you'd still be on your original pump had you not ran the tank low on a regular basis. In any case, it's good to know that our Rivieras have a pump with a hearty design, and have a great record as far as durability goes.