Why topping off your tank is a bad idea

https://www.automoblog.net/topping-o...your-gas-tank/

And

Why You Should Always Keep a 1/4 Tank of Gas in Your Car

https://www.yourmechanic.com/article...-cheryl-knight



Opinions?

 

The article regarding keeping the fuel level above 1/4 tank: unbelievably badly written. Yes, it is absolutely true that the fuel pump when mounted within the tank is cooled by the fuel and it is true that repeatedly running the fuel level to near empty can damage the fuel pump - this is the most common cause of pump failure.
But the writer of this article seems to be confused and therefore causes confusion. According to the writer, modern fuel pumps are mounted WITHIN the engine (WHAT…??….). It is true that engines that use high pressure fuel pumps (as on the F-Type, for example) have the pumps located in the engine compartment as elements of the fuel system….but within the engine? Like the crankshaft, the pistons….?
ugh…
but yes, good advice to fill up by the time the tank level drops to 1/4.

 

I guess it depends on where the price of gas is going: if rising, top off before it goes higher; if dropping, which it is for just a moment, let it run down so you can fill at lower price.

Come on: common sense says don't run out of gas and after 25 years cars have lots of dirt in the tank which you might not want to suck up . . . or destroy the fuel pump in the tank.

 

Mom used to regularly run the tank almost to E. Dad would tell her it doesn’t cost any more to keep the top half full.

 

On the Jaguar direct injection (V6&V8) engines, the 2 high pressure fuel pumps are located on the side of the block. The god awful turbo 4 cylinder has 1 mechanical FP on the back of the camshaft. Inside the (V6&V8) engine is a counterbalance shaft setup that also acts like a camshaft for the 2 mechanically operated pumps. There’s still an electrical FP inside the tank. As long as you don’t go below 1/4 tank too often, the in tank pump should be fine.

 

My XJ8 now has ~ 95K miles.
In 2012 @ ~ 65K miles, I had Jaguar replace the single fuel pump. I was told if I had an XJR I would have 2 fuel pumps. Cost me $1,005 + $115 for the tow.

Now that I have learned to not let tank get below ¼ tank, which I used to do occasionally, I wonder if this pump failure could have been avoided.

I also used to always top off the tank filing up to the nearest 5¢ & sometimes more. Mostly seemed OK & sometimes I’d go too far & some fuel spilled into the scupper.

Now I wonder if this is the reason I occasionally get a fuel smell in the cabin when cold start.

Until last week, I had never heard that these 2 habits could be harmful.

Previously, I thought the dangers of these 2 habits were spilled fuel/wasted $ & running out of gas.

 

Yes, as a retired ink-stained wretch (journalist/writer) I can say the second article on fuel pumps was very poorly written. Then again, it was on a commercial site soliciting you to call and pay a mechanic for phone help. They got what they probably paid for in generating the copy.

I am habitually guilty of both topping my tank off to squeeze in as much fuel as possible and running the tank low. Typically, I let the low fuel light comes on, then fill it within 10-20 miles at a nearby lowest-cost top tier fuel station. In the main it won’t take more than about 18 US gallons at that point unless I force it. I don’t think I’ve ever put more than about 19.5 into this car, which gives me the nagging thought I might have the Euro-spec tank.

That aside, I don’t want to pay to repair the canister system or burn out a pump, so I once again have been told the error of my ways and will try to behave. The articles were a good reminder of the penalties involved.

 

I've replaced so many in tank fuel pumps to either full or empty tanks. Usually intank fuel pumps seems to stop working just after tank is filled up. It is ridicilous to think that pump breaks more easily when the tank is under 1/4 capacity. Fuel flows through the pump when it is pumped. Pump sits in the plastic casing what is working as a suction cup. 1/4 is not only "paint" in the bottom of the tank. I understand the dirty tank issue with low fuel level. But even if with dirty tank is filled up with fuel. The fuel is dirty and the gunk will get to the pump anyways. Usually fuel return is fed to the pump casing. Return fuel is warmer or even hot to touch (60'c) with normal fuel pressures.