At The Pumps

BlackOut V8 · July 26, 2009

I have been using Shell V-Power 93 for the last four tanks. My truck was getting 16mpg and then went up to 17mpg the next tank. At this fill it was 14mpg!!! I couldnt beleive that it went down this much. I was expecting it to actually go up slightly because I have just replaced the plugs with NGK TR5 Platinums gapped to 0.40 and also replaced the fuel filter. The only factors I can think of are:

1) Heavy on the throttle (which I have been) because the truck is running good.

2) The NGK TR5 Platinum plugs with different 0.40 gap then the stock 0.60 gap Ac Delco Platinums

3) The fuel filter has a slight leak

My plan is to keep off the throttle to get a better and more accurate mpg reading to see if the plugs or the filter are the issue.

Can getting on the throttle too much cause a 3mpg decrease? Do I have the wrong spark plugs? Should I be running the Ac Delco plugs? What about the fuel filter??

PLEASE help me out!!!

Any input would be great

BlackOut V8

kntharty · July 26, 2009

you forgot all of the above that makes the most sense to me why did you choose to gap different than recomended

BlackOut V8 · July 26, 2009

I did not gap the plugs different. For the stock 2003 Silverado the plugs were originally gapped to 0.60, after tests the new recomendation is 0.40 gap.

SO

Why would my gas mileage go down from new plugs then? Should I be using Ac Delco plugs?

2000DV4.8 · July 26, 2009

Go through a tank with a more moderate driving style, see what your mileage is, then worry about something being wrong with the new parts.

BlackOut V8 · July 26, 2009

Go through a tank with a more moderate driving style, see what your mileage is, then worry about something being wrong with the new parts.

exactly what I was thinking

Zembonez · July 26, 2009

You are not the first person that has had issues running non OEM plugs. I tried a set of Bosch Platinum (thinking I was upgrading) in one of my trucks and it did the same thing. Don't ask me why... but I switched back to the OEM plugs and it wsnt back to normal. I've also heard similar stories from other truck owners.

66nova · July 26, 2009

I have been using Shell V-Power 93 for the last four tanks. My truck was getting 16mpg and then went up to 17mpg the next tank. At this fill it was 14mpg!!! I couldnt beleive that it went down this much. I was expecting it to actually go up slightly because I have just replaced the plugs with NGK TR5 Platinums gapped to 0.40 and also replaced the fuel filter. The only factors I can think of are:

1) Heavy on the throttle (which I have been) because the truck is running good.

2) The NGK TR5 Platinum plugs with different 0.40 gap then the stock 0.60 gap Ac Delco Platinums

3) The fuel filter has a slight leak

My plan is to keep off the throttle to get a better and more accurate mpg reading to see if the plugs or the filter are the issue.

Can getting on the throttle too much cause a 3mpg decrease? Do I have the wrong spark plugs? Should I be running the Ac Delco plugs? What about the fuel filter??

PLEASE help me out!!!

Any input would be great

BlackOut V8

Absolutely!

I agree with Dan. Stay off the throttle for a tank and then compare. Even then, one tank of gas is not enough to compare to see if a change helped or hurt mileage. Too many other variables. To accurately compare fuel mileage. Make a log of a number of tanks.

There are too many changes thank can effect mileage, ie...Temperature, traffic, idle time, hot rodding, number of passangers, weight in the bed, and so on.

2000DV4.8 · July 26, 2009

Also, on this last tank, were you using the A/C more? Has the weather been any different? All of these can play a role in fuel economy. Do you top off your tank when you fill up, or just stop when it goes "thunk"? Filling up at the same station/pump each time?

BlackOut V8 · July 26, 2009

The conditions have been the same throughout all tanks. I fill at shell always and do not "top off" the tank. Just until the nozzle disengages. I was using an agressive drving style and on the throttle a lot so I think this may have caused a lot of the decrease but the plugs worry me with the mpg. The truck accelerates well and has lots of power. At a stop light the rpm gauge reads 500rpm constantly and the needle never spikes or jumps at idle. The idle does "rumble" inside the cab a bit but I think this is just the motor rumble at idle not the plugs causing it??? My current plan is to drive a more moderate driving style and see what the mpg is. I will keep everyone updated.

What about the plugs though?! Do these trucks really require the factory Ac Delco plugs? Anyone have similar mpg issues with Ngk TR5 plugs?

THANKS GUYS

BlackOut V8

belchfire · July 26, 2009

In addition to the good advice you've received above, let me add that I've experienced a significant difference in the delivery of fuel from different pumps. I know the commissioner of agriculture (Georgia) regulates and inspects gas pumps, but there must be a tolerance limit. I fill up at the same pump day in and day out, and my fuel quantity matches the fuel used on my scan gauge. When I go to a certain pump in town, I'm routinely showing 4 or 5% more fuel added than the scan gauge expected. It figures since they're cheaper.

Are you using the SAME pump you used for your 87 or 89 octane? Using larger quantities of fuel for your tests helps to wash out issues like this. When I make a change that I intend to measure, I usually ignore the first tank and make sure the second tank I measure is at least 3/4 of a tank before I start measuring. Then I try to measure several tanks in a row.

Zembonez · July 26, 2009

I've put 6 gallons of gas in a five gallon can on Padre Island before... I'm guessing their pumps were a LITTLE off.

brims · July 26, 2009

Just a wee bit.

BlackOut V8 · July 26, 2009

Yeah I have used the same pump and it is always right full. I think I found the problem. My foot!!

66nova · July 27, 2009

Yeah I have used the same pump and it is always right full. I think I found the problem. My foot!!

From reading your sig, I don't see a custom tune listed. If you really want to change you mileage you need to visit this website www.blackbearperformance.com

Take your throttle body spacer and put it on ebay and use that money towards a tune. A custom tune promises to drop your mileage by 2-4mpg because you will have so much fun using the extra power. But seriously if you can keep your foot out of it you will most likely gain a couple.

cujo8 · July 27, 2009

I have been using Shell V-Power 93 for the last four tanks. My truck was getting 16mpg and then went up to 17mpg the next tank. At this fill it was 14mpg!!! I couldnt beleive that it went down this much. I was expecting it to actually go up slightly because I have just replaced the plugs with NGK TR5 Platinums gapped to 0.40 and also replaced the fuel filter. The only factors I can think of are:

1) Heavy on the throttle (which I have been) because the truck is running good.

2) The NGK TR5 Platinum plugs with different 0.40 gap then the stock 0.60 gap Ac Delco Platinums

3) The fuel filter has a slight leak

My plan is to keep off the throttle to get a better and more accurate mpg reading to see if the plugs or the filter are the issue.

Can getting on the throttle too much cause a 3mpg decrease? Do I have the wrong spark plugs? Should I be running the Ac Delco plugs? What about the fuel filter??

PLEASE help me out!!!

Any input would be great

BlackOut V8

I'm running Denso Iridium plugs using the stock Gap setting w/ o any problems. How do you know your fuel filter has a slight leak? What year truck are you driving? I believe my fuel filter is in my gas tank, but don't quote me on that. I have a blackbear tune and I am getting 20 MPG routinely, but that is mostly highway driving at 55-60MPH. Before the BB tune I was getting 16-18MPG, but your driving style will determine your fuel economy.