Think I can just spray some brake cleaner on it?

 

When I changed the plugs, I was told not to gap them as they were pre-gapped. It was some Bosche brand two prong thing-a-ma-bob plug on sale. Even if I did gap them, I don't think it would have been accurate since most normal gapping tools wouldn't be able to get in to the right locations

 

I would not advise it. You would be better off using an electrical cleaner.

 

Hmmm Interesting... This did seem to happen with the formulation of winter gas. Now that winter is over, the gas is going back to normal ove the next few weeks.. I'll have to keep track of it

You'd think though that being in San Diego, there would be no such need for "Winter gas."


Thanks everyone for the suggestions.

 

There are some electrical cleaners that leave a "Protective" resedue. Make sure the can states Non-Residual. No Resedue.
No to carb or brake cleaner. Yes to CRC Contact cleaner.
Remove the MAF from vehicle.
Do not remove screen.
Note the color of the intake side of the elements first with a flashlight.
Spray like heel and look again.

Good Luck. Hope the prob is this siimple to fix.

 

Hey may hve a longbed, the most I have gotten on the 5.3 is 425 I think ECSB. I was amazed. 270 is terrible I am at 270 right after half a tank.

 

It's a '01 Suburban

 

I get 240-260 a tank and then $2.40+ a gallon to fill it back up . Average MPG since new..... 9.7 . It's definetely better on summer formulation gas more like 280-300, but in the summer I tow a lot so it ends up averaging out to about the same. Towing my trailer gets me about 150 miles per tank (6-7 mpg) . I am about due for plugs, and will be checking/cleaning the MAF as well but I don't expect much, the truck has been a dog on mpg since it was stock, 6.0L + (6,000+lb/lifted/geared/supercharged) = mpg.

Your problem sounds like it may be the gas, 450 miles per tank down to 390 is about a 14% loss, that is exactly what I get on the switch from summer to winter gas, (280 down to 240 = 14.3%) It starts mid-late November and lasts till about May-June.

 

4.10 Gears, 6.0 and AWD make for ugly mileage. I only get 14mpg or so on the highway at 75.

 

I too have been getting bad milage. This is on a 04 GMC 5.3 reg cab 4x4. If I am lucky I might get 335 but here latley has been around 270. Sometimes I can get 200 at a half of a tank but latey has been 150-170. Just dont know what the deal is.