Originally Posted by FujativeOCR
I never ran mine at full throttle early on. Maybe that's my problem?!?
Very well could be.
I've owned around 100 or so different vehicles the past (36) years so I have a lot of experience with this.
Yes, today's machinery and quality control gives very precise measurments and clearances between metal parts. So today's engines are not as "tight" as the used to be when brand new.
However, the piston rings NEED to time and compression to EXPAND against the cylinder's walls to create optimum SEAL. The tighter the piston ring/cylinder wall SEAL, the less compression is LOST.
That said, I drive my new cars relatively hard and a WOT frequently. Highway ON ramps are a great place to do so!
I bought my 14 Compass w/2.4 with 400 miles on it. After I bought it, I too was NOT please with the fuel economy AND the loud "growling" type noise emitting from the engine upon acceleration.
I started noticing the engine becoming "looser", more responsive and increasing in MPGs around 2,000 miles or so. The engine also quietied down on acceleration.
Around the 4-5000 mile point, I noticed the engine is MUCH MORE responsive (all over the RPM band), much quieter when accelerating and getting VERY GOOD fuel mileage.
It's at 5,500 miles now and gets high 20's consistently on the highway. I believe (30) MPG highway is very obtainable IF I could keep it at 65 MPH.....which I can NOT seem to do! LOL!
So IMHO, drive it like you stole it as soon as you get it off the dealer's lot! Well, not quite THAT hard, but you get my point.
Like others have stated above, do NOT baby a new engine! Your risk NOT getting that piston ring/cylinder wall seal to the optimum level.
BTW, have you ever watched NHRA engine builders rebuild an engine (from scratch) during an event ? (pretty freakin amazing BTW). Do they go out and "baby" that engine when the first fire it up ?? HELL NO!