How Many miles per tank do you get with 1998 Suburban? maybe its called the k1500 350 engine?

I have a 89 4x4 V1500 Burb that I have had since new with a 40 gallon tank. You cannot burn it dry and typically I have 6 to 9 gallons left when I run in low on trips between fills. The fuel pump is cooled and lubeb by fuel in the tank so it is not wise to run it low all the time. I have gottn a little over 600 miles for a fill a few times on long trips if I run it low (averaging 17 to 18 mpg) and 500 mile with a god reserve it no trouble at all.

Per snipped-for-privacy@gmail.com:

On my '98, no way.

600 miles on a tank is about max, but I think about filling as it approaches 500. Typical MPG on a round-trip to the beach (about 190 miles) is 14.something. That's with a rooftop box and roof racks.

Per other threads, it doesn't do the fuel pump any good to run the tank almost dry - supposedly because it relies on the fuel around it for cooling.

Damn, it must be nice getting 500 miles a tank of gas, I got a 99 Jimmy and I only get 15 mpg on a good day with a 4.3 v6

Don`t ever believe the mpg ratings until you drive it. Acording to my info on my truck,I should get 400+ on the freeway.Didn`t even get close to that.I got just over 300 and it was on empty.

Try better octane fuel as in a 9 to 1 CR or higher engine, 87 can murder the mileage as the ECM retards the spark to control kncok. I can consistantly get 17 to 18 MPG on trips with my 89 4x4 burb with 175 K miles on it now. I never use 87 and raely use 89, it is usually 91 or better in it as performance and MPG suffers when I use lower octane fuel.

Per TheSnoMan:

Ever crunched the numbers? i.e. is the additional cost per gallon cover gallons saved?

My '98 gets even worse mileage than most others report - but I lay some of that to all the junk I have on the roof.

OTOH, somebody somewhere opined that the occasional tank of premium would have some effect on the vehicle's onboard 'puter and improve mileage when running 87.

I am surprised as i always get 18+ mpg on steady trips and with 92000 miles, i have never used anything but ARCO 87 octain gasoline. I have been through all the western states and never a miss.(except a battery connection problem) old john

1999 Tahoe. 1989 ford fs bronco 2000 xj cherokee 1988 xj cherokee 55cj5 with a chevrolet 350 an FC!50 jeep /302 ford engine all on 87 octane oj

Yes I have, never got over 15 on 87 when it was new and performance sucks with 87 too. Even if MPG was not better I would still use it because it runs much stronger and crisper on better gas. It is not like the old days when it was obvious when you needed better gas (engine knock was apparent) Today, with knock sensor and ECM retarding spark it is stealling your MPG and performance from you quietly because it only knocks now when it exceeds the abilty of your ECM to control.

Also by what logic is a occaision tank of 87 going to improve 87 performance and MPG?? As soon as you fill it up with 87, the ECM here the knock and goes back to retarding spark the instant it hears it. The only reason that there is a knock sensor is so to limit consumer complaints about motor knock on 87, no because of emissions or that 87 is the best fuel. If 87 and 89 was removed from market, (especailly 87 which was intended for engines with about 8 to 1 CR or less in mid 70's) they could even remove knock sensors for a lot of engines

Per TheSnoMan:

That was my reaction too - and the reason I never bothered to try it.

I meant to say a occasional tank of 91 octane improving 87 performance.. The ECM hears the knock as soon as low octane fuel hit engine and the edge is lost. I recently picked up a real time graphing scanner to monitor engine performance (airflow. manifold pressure, fuel flow, times and so on) and I am going to test drive some new vehicle with it plugged in and "listen" to the engine on low octane fuel. On my 2000 5.7 is show no spark knock retard at all at any time (because I use good hi octane fuel)

You are partially correct but maxium power and economy is achevied when peak pressure is achive at a certian point in the power stroke of the engine and lower octane fuel that has to have its spark retarded lower the peak pressure and changes the point at which it occurs which lowers efficency and peak power. When the ECM hear lnock, it will retard it a lot (15 to 20 degress and then slowly start dailing some back in until the point you mention is found but by its presence and need to retard the spark, you are reducing engine output and MPG at any given speed. My

300 K3500 shows between 30 and 35 degress of advance in normal driving and almost 20 at a idle and shows no knock activity at all and it runs good but then like I said, it never sees 87 octane fuel either.

I could not agree with you more as power will increase because injecting fuel at last second into chamber it cools mixture allowing higher CR ratios without knocking and more power and better efficency. Furthermore, less fuel is lost to savanging os gasses when valve overlap so more MPG gains too. Overall when it hits main stream, the line between diesel and gas economy if going to get a lot blurrier and diesel will loose more of their appeal.

David Johns> Hopefully sometime in the near future we will see direct cylinder injection