Royal Purple oil change. Mpg dropped!!!?????

[GrandpaSnugglz]

Like everyone I'm on a on going search for better mpg. My first oil change I switched to synthetic(5w) I did my second oil change about a month ago to Royal purple synthetic(10w) and my mpg has dropped. About 1.5, from 15mpg to 13.5!!! I've been hearing this is the best stuff in the biz and heard of folks getting a tad but better mpg from it. I don't get it. Is it because I went to 10w? I can't imagine that's why though. And ideas?

 

[Mopar_Express]

Going to a heavier weight oil could definitely have an effect on your mileage. Im willing to bet if you switch back to a 5W youll get that 1.5 mpg right back. The factory recommends a relatively light weight oil for a reason. Why did you switch to 10w?

 

[Arctic-Rodz]

What year is your truck?
I think the weight of the oil might be the issue also.

 

[TXKID]

I used royal purple 5w 20 and my mpg's went up

 

[GrandpaSnugglz]

Ive always switched to 10W-30 in the summer, it has less Viscosity index than 5W-30. And less VI means fewer engine deposits. I can't imagine the small up in weight changing mpg this much or even at all.

 

[Mopar_Express]

Did you change anything else at the time of switching to the 10W? If not what other element would be changing your gas mileage? There could be a ton of other reasons your mileage may have decreased (different driving, more idle time, climate change, etc) but if you havent done anything different other than adding a heavier weight oil thats the only thing it could be. Royal Purple is considerably better than most other oil options out there and it has some of the best properties and additive packages. It also has a high moly content which means even if you stuck with a 5W you shouldnt have to worry about deposits.

*Also in your previous post you mentioned viscosity index of the 10W-30 in relationship to the factory 5w-30. I can only assume that was a typo as the factory recommended oil is 5W-20? I just want to make sure you're comparing the right apples and oranges.

 

[emjohn4]

Ive always switched to 10W-30 in the summer, it has less Viscosity index than 5W-30. And less VI means fewer engine deposits. I can't imagine the small up in weight changing mpg this much or even at all.

Yes - oil weights will make a difference in MPG.

Factory recommends 5w-20; and you put in 10w-30. Thicker at both initial startup temps and operating temp.

I'm not shocked you MPG dropped with the change in oil weights.

Your MDS won't likely work as effectively or smoothly with the 10w-30 either.

 

[GrandpaSnugglz]

Nope all the same driving in the most part beside , hot humid weather and lots of rain. Just saying I've always down the summer switch and never had this issue. It's just wacky that I had this large of a drop on such a prestiges motor oil.

*not a typo mopar_express. The VI is less. And yes 5w is factory, it's satisfies a larger amount of engines in the large amount of locations and situations. Hot, cold ect. But do you where sweaters and jackets year round? I don't, I change my threads depending on the climate, like wise with my motor oil.

 

[scHemi]

I would put 5w-20 back in and see what happens. Your probably messing the mds up with the thicker oil

 

[Mopar_Express]

*not a typo mopar_express.

I was referring to the 30 in 5W-30 as the typo , because the factory oil is 5W-20 Sorry I should have been more specific there.

The logic of changing your oil for the seasons is sound, however each vehicle is different and will give different results in each application. The way I see it is that the manufacturer does extended testing on the motor and vehicle in all kinds of conditions hot or cold. If they want to put in the manual and stamp on the oil cap that it takes 5W-20 thats what i'll put in because I can only assume that good data and lots of research go into that decision.

Maybe it would be worth trying another cheaper brand of 10W-30 to see what kind of effect that has? All we can assume based on the information that we have is that its either the oil weight or the brand that tanked your gas mileage and lots of guys, myself included, are running Royal Purple with nothing but good results. Id definitely be interested to see if you had different results with a different oil.

 

[Burla]

Gramps!! Yes man going from 5w20 to 10w30 will absolutely make your mileage go down. Next time run RP 5w20 and watch the difference.

 

[Strange Ram]

No offense intended... but you are getting good advice here..

Used too... back in the day... in much older vehicles, swithing from summer to winter oil was normal. So was adjusting your points... changing oil much more frequently... cap & rotor.. ect.

Those days are over. This is a modern vehicle. Many many millions of dollars went into designing & testing new technology that is built into your truck. You cannot treat it like it was made in 1970.. or 1980. Just because you've always done it, doesn't mean it is correct to do it now.

You truck was designed to run with 5w-20. Not 5w-30... or 10w-30. You are trying to force 1970's thinking into something that was made in 2012 (or thereabouts).

It'd be no different if you got upset at your truck for not accepting an 8 track or cassette tapes.

Use what the book says... 5w-20. These engines are tested to near destruction to come up with these recommendations. Using RP in 5w-20 would be great for your engine. Using a heavier weight is going to cause problems.. maybe major ones.

 

[Xtreme545]

Pretty sure your MDS will not function correctly at a heavier weight, I'd go back to 5w20


Sent from rock using chisel and hammer

 

[GrandpaSnugglz]

Yeah I guess I goofed. Will be doing an extra early oil change next weekend. Thanks for the schooling fellas

 

[Strange Ram]

Let us know how it does!!

 

[cux211]

yeah bud if you tell the techs at the dealer you put 10-30 in there they're liable to pitch a fit the tolerances in these new motors are much tighter than they used to be in the older engines you WILL NOT get proper lubrication with heavier oil and can/will cause premature wear of internals

 

[smiley]

The only number that matters is the 20 the lower the first number the better no matter where you live as wear happens at startup almost always. The best mileage will be with 0W-20 and can be used with MDS no problem because it is only thinner at startup and same as 5W-20 at operating temp. There is no reason to run more than 5W and what killed mileage is the 30. We have talked about this many times on the forum and I recommend anyone be careful if not sure differences as it can and likely will cause harm longterm.


$miley