Hey guys I have a 99 3/4 ton 360 with 4.10 gears and have heard and read about plenium gaskets, my question is when one is bad or going bad does it give off symptoms??? My gas mileage SUCKS!! I recently tuned it up with new plugs wires and cap and button which helped a little but I still only get around 10mpg which includes town and some interstate. The truck is 100% stock with the exception of a K&N cai. The truck runs good without any issues and only has 108k on the odo, I just would like to get some better mileage if possible. I appreciate any thoughts you have especially on the gasket, maybe mines bad and I do not know it??? Thanks.............

 

plenium gasket can give you bad mpg and a leak gasket can clog the cat a mess with the 02 sencors also,,, thoses are the thing the same to go bad and hurt mpg the most..

have you looked down the tb or did the vacunm test?

 

symptoms are oil loss, pinging under load, excessive sluggishness, puddle of oil on top of belly pan.

i don't know that it contributes directly to poor mpg. mpg tends to suck either way. my mpg didn't really change noticeably either way. i get fair on the hwy 15-16-17, and it sucks in city 12-13-14.

try yours on nice steady extended highway drive at 50-60 with OD on and see what you can get. that'll be the best it ever gets.

 

I have done this a zillion times (so its seams) since I bought my truck brand new, and the kaka has never ever EVER got much over 14 MPG. Have never seen 15. And I check the mileage religiously at every fill-up, which is always about 12. How the heck do you guys get up in the mid teens?

I was just figuring the other day, I have pumped over 13,000 gallons of gas in my truck... A few extra MPG sure would have saved me some coin over the years.