Change in MPG

[KenR 955]

I'll start out with some info.
2014 Ram 1500, 5.7, 8 speed, 107K miles
( I know the digital display is not perfect, but for this example, it is the measuring stick)
Digital display showed 19.3~18.9 mpg when I bought it 2 years ago, with 89,500K miles on it.
For the last 1.5 years, I've been averaging 18.5~19.1 mpg. In the last 6 months or so, mpg has dropped to 17.5~18.1.
Tires were just changed from Goodyear Wrangler sucks-a-lot to Adventuro GT highway treads. Ride became much more firm, (I assume the tires construction has much to do with it), psi is 40lbs in all 4 corners, but MPG is now down to 16.6~16.8. I have not changed my driving habits and here in Tn., we don't have winter style gas as did NJ. Recent O&F (Redline 5w30) and I am waiting on Blackstone"s report.

I guess the question is, am I looking at some engine issues? What might affect the MPG this drastically? The air filter is clean, and I'll screw some spark plugs into it next week if time allows. No idea it's service history.

Ideas? Thoughts?

Thanks again
Ken R

 

[indept]

So they might be the original plugs so make time to change them before wasting money on other stuff. That might be the problem.

 

[huntergreen]

I am guessing your tires are heavier than the tires you replaced which could account for your mpg loss.

 

[KenR 955]

I am guessing your tires are heavier than the tires you replaced which could account for your mpg loss.

I agree, or the new tires have more rolling resistance.

 

[Loudram]

I agree with the above. Change in tires and/or needing a plug change.