All of this oil talk today (mostly to myself) has got me thinking:

Could it be for all of the people getting abnormally bad gas mileage with their H3 due to perhaps conventional oil being put in their engines instead of Synthetic?

The H3 requires synthetic oil. Are any of you guys (or gals) that are getting the 10 to 12 mpg mileage with your H3's taking them to a oil change place, like a Jiffy Lube? If so, maybe the reason for the bad mileage is that they are putting in some crappy oil, or the dealer is doing it. It says right in the manual that Synthetic is required.

Could that cause such a drastic drop in MPGs? I know that not changing your oil for an extended period of time can do that, one the viscosity breaks down.

Also, doesn't the H3 recommend 5w-30? If they put 10w-30 in there, that would also cause worse gas mileage. I could be wrong about this one, but unless I lived in the desert, I don't see needing 10w-30, especially synthetic.

Well, I guess I'll find out this weekend when I put 5w-30 full synthetic in and an K@N Oil Filter. We'll see if the performance goes up at all.

 

I only have 3500 miles on mine and she's still drinking the factory oil.

 

Well, if you know your stuff mechanically, and I was in your shoes, I would change the oil with some full-sythetic stuff. You never know. You probably should change it anyway since it's 3500 miles and still running the factory oil. It's probably about time.

 

I use the Pennzoil Premium synthetic 5W30. AC Delco oil filter and am running close to 20mpg on the highway. I also use the oil monitor system and get close to 12K miles between oil changes.

 

I don't trust that system anymore once I did the research into how it works. It doesn't actually sense your oil condition, but rather calculates what it predicts is your oil life based on engine speed, temperature and mileage. It keeps track of your engine temps and rpms at all times and predicts what it thinks your oil life is. There are no sensors that actually touch the oil and sense what condition it's in (like I thought it did before I did the research).

 

I changed mine at 1000 miles with Castrol Syntec...Then again when the clock said 5000 miles..

 

i only use mobile one full synthetic. I'm gonna change the oil in it once I bring it to the dealer for this mpg issure. I don't see oil causing the mpg to be 6 mpg below sticker though. I'll force the dealership to at least give my pcm a flash, if they don't find anything else.

 

A varience of 10w-30 to 5w-30 wont cause a severe depreciation in mph. Clean oil, air/fuel mixture, clean oil filter, clean air filter, weight of the vehicle, tire pressure, aerodynamic drag, and how you drive will all impact the mph of your vehicle.

 

I only use mobil 1 and my milage is at 12.5. it did not get any better after draining the factory fill and putting in synthetic.

 

My take on the low mileage is this: The H3 is a fairly heavy vehicle with a smallish engine that's geared for fair economy at cruising speed. The problem is, it takes a LOT of throttle to accelerate, so stop & go driving mileage is terrible. Drivers who rarely get on the freeway, or are more prone to "aggressive" driving are really going to get hammered hard on mileage. Not many mid-size vehicles exhibit such a huge spread in real city/highway mileage. Though the 3.2 gets the H3 the coveted 20 highway mpg rating (and really gets it), I think it would have much better all-around mileage with a larger engine that didn't have to work so hard just to get the truck rolling.