I tried an expensive experiment over the holidays. Knowing I was about to take a 3000 mile round trip to visit relatives I decided to change out all my fluids to Royal Purple in my 06 hemi megacab, hoping for a slight mileage increase. In a trip that long any improvement would make a difference. Well after a lot of driving, listening to my wife and teenage daughter complain and whine, and MANY stops at most rest areas between Jacksonville, Florida and Olkahoma City, Oklahoma my mileage only changed when I actually slowed down. At 80 I averaged 15.6mpg, at 70 it was 16.8. Higher than 80 and I didn't want to know. No change from the over $200 fluid change. Engine oil, automatic transmission fluid, and rear gear lube were all changed.
Gas prices varied significantly, too. $1.68 at home, $1.77 in Louisiana, $1.40 in Oklahoma City. All regular grade. I even tried different grades of fuel out of curiosity, but no change there either.

 

I did the engine, both diffs and transfer case in my Jeep Grand Cherokee in Oct. of '07 with Royal Purple. The Jeep was bought used from my in Aug. of last year and had Dino oil (previous owner ALWAYS had work done at dealer) in the crankcase and whatever they use in diffs.
I saw an immediate and permanent 2+ mpg increase. I've since gone to Royal Purple in the truck (engine only, the diffs are not due for another 4k miles) and sadly, have not seen any increase in fuel economy. I'm going to stay with it though, as I now change my oil at 6k instead of 3k, and think the engine sounds a little smoother with the RP in the engine...

 

oil doesn't need to be changed at 3kmi if your highway or not towing. You can go 5kmi no problem on dino oil as most manufacturers even reccomend. 3kmi is old school changes. Synthetic can go even 10kmi between changes.
Ofcourse if your constantly working the truck I would change sooner. My wife's car says every 5kmi along with all other newly built cars and that's with dino oil.
Oil doesn't break down, it's the cleaning agents in the oil that break it down and the sludge.

 

My wife's Honda is 10000 miles /1 year between oil (3.5 quarts of Dino) and 20000 miles between filter changes. This 3000 and 6000 mile change interval is crazy but you have to due it to keep your warranty. I due 6000 miles / 6 months with synthetic and call it good.

 

even if the book says it i would change the filter everytime i changed the oil..I did this one time leaving the oil filter on for to oil changes because i added the oil before i changed the filter so i left it in thier..well to make a long story short the filter started coming apart inside..didn't tear anything up but i want do that again

 

The oil, especially a good synthetic will outlast the filter. If anything, I'd change out the filter and top off the amount of oil lost before I did it the other way around.

And to answer the 'dog, I agree that today's oils in today's engines don't need to be changed like in the old days, but personally, I do a bit of haulin' and more importantly, when I'm home in Ga., at least half my driving is on hot dusty dirt roads or off-road. Combined with a CAI (even though I have a pre-filter over it) I find my oil gets fairly dirty faster than the average driver. Besides, better safe than sorry...

 

If Honda is anything like Hyundai, then the oil filter that goes in my wife's V6 Sonata is strickly a paper filter. There are no springs/check valves..etc... It's a canister on top of the motor that has a plastic heavy duty cap. This ca has a plastic insert that you slide the filter on/off of. I refuse to change the filter every time her oil gets changed. I change her oil every 3kmi because she has remote starter and that makes her car run for 20minuted every morning and before she leaves work. If you call it 30minutes of idle everyday, I figure that as 900miles at highway driving consistency every single month. Otherwise I would change it at 5kmi.
She just loves that starter...lol
If your ever at the parts store, look up 2007 Sonata V6 I think it's a 3.3? Check out the oil filter and you'll see what I'm talkin about. At nearly $10 a rip for the basic one too!

I don't think Chrysler set the oil change for the Rams at 3kmi, I think it's 5kmi?? I have to check the manual.
And if you need to do that to keep the warranty, they have to prove it was lack of oil changes, you don't have to provide receipts! If you did and used full sythetic, they would void warranty because the lack of changes even though you went with synthetic. It's all a game....

 

Before my switch to Royal Purple I had Dino, or whatever the dealer puts in. I think the rear end is synthetic from the factory, but I could be wrong. The manual says 3000 miles for engine oil in city driving, 5000 for strictly highway. The rear end lube is supposed to be changed at 30,000 regardless, according to the book. That seems an awfully short time for the rear to me, but having read some of the problems some people are having, a quick inspection at the same time couldn't hurt! I just passed 43,500 miles on my trip, and all fluid changes have been done under the severe service schedule, mostly by me, occasionally by the dealer.