Your Gas Tank: Do You Top Up or Not?

[quagmire]

I have actually read a lot of articles lately that say if the car calls for premium, its really optional. If you elect not to put premium in you aren't hurting the car - at worst you are giving up a 5% or less in horsepower and nothing in MPGs. Even in a 300 hp car we are talking 15 hp which will not be noticeable. Premium gas tends to be "recommended" in higher compression engines to avoid "knock." Since modern cars have pretty sophisticated knock sensors that detect this and retard the timing (hence the ~ <5% loss) it's a non event.

On the other hand its not a huge difference in the price of a tank. The real savings is probably prevalent when you drive a lot of miles per year (say 20K like I do), your car gets lackluster economy, and the price of gas is high (like a couple years ago when it was >$4 a gallon - the percentage difference between 89 and 91 in price can start to become a significant amount).

Yeah, cars these days do have knock sensors that adjust the timing of ignition, etc when the idiot puts regular in a vehicle that recommends premium. But, it does hurt power and MPG because the engine isn't burning the gas it was designed for and is adjusting its timing to prevent detonation and the fuel is not burning at optimum efficiency. Like I stated, I wonder though if the difference knocks out the savings.

Also, it doesn't matter if fuel costs $4 a gallon or $2 a gallon, the difference will remain the same just as long as the cost between regular and premium remains 30 cents per gallon. The highest difference I have seen between regular and premium is 50 cents and that only increases the difference by $1.50. There is zero excuse not to put premium gas in a vehicle that recommends premium.

Just put the fuel your car recommends in the tank. Fuel is not an area where you can cheap out on when it comes to your car.

 

[renewed]

I always put gas in it if it ever gets to 1/4 of a tank. Not always fill it up though. I NEVER let it get below 1/4 of a tank though because it is terrible for the fuel pump, especially with how hot it gets down here.

 

[skunk]

I always put gas in it if it ever gets to 1/4 of a tank. Not always fill it up though. I NEVER let it get below 1/4 of a tank though because it is terrible for the fuel pump, especially with how hot it gets down here.

Exactly what I do: my fuel pump suffers if the tank gets below 1/4 full: some people even drill a 1/16" hole in the filler cap to relieve the low pressure. Mine's a 2.5L BMW intercooled turbocharged diesel, a version which always suffered from a weak fuel pump. I always fill up, though: petrol stations are not places you want to visit any more than absolutely necessary.

Mind you it costs me over £80 to fill up, so it helps to ease the pain, too...

 

[macquariumguy]

I almost always wait until the low fuel light comes on and then fill until the nozzle clicks off.

 

[spencers]

I fill the bimmer up when the orange light comes on. 93 octane or better. I usually go for ethanol free, as well.