I checked in my haynes manual and it says that the oil should be 5w-20. On my oil cap, it says that it should be 5w-20. Looking on my receipt from my last oil change from pepboys ( sons of bitches...) it says that they used 5w-30 instead of 5w-20. Could this have anything to do with my loss horsepower? Or does the viscosity of the oil not matter?

 

If this is a 1500 (non-Mega Cab) then it's an MDS and it IS VERY viscosity specific for proper MDS operation, so much so that there is a sensor for oil viscosity and a dealer can tell if an improper viscosity oil was used and THEY WILL void warranty coverage on the engine if they can tell that improper oil was used - especially if the problem is specifically MDS/Lifter oriented.

Non-MDS not a problem as my '04 actually specs 5w-30 although I've used 5w-20 in it depending on time of year (air temp) when I've changed my oil. If you have a Mega or 2500/3500 (non MDS versions of the Hemi) then don't sweat it.

Now I know some guys will chime in and say that they've used 5w-30 in their MDS trucks and have not had an issue, but if it were me, I'd get the 5w-30 out of there and put the recommended 5w-20 in. I'd go back where you had it done and b*tch - and I'm sure they'll tell you it's no big deal - but according to the manufacturer and their engineers - IT IS...

To answer your other question, oil viscosity plays a role in performance - thicker oil offers more resistance to moving parts, back in the old days of wider variances in engines and when most V8s spec'd 10w-40, I'd routinely go to 20w-50 as the engines got older - less blow-by and it wouldn't leak through marginally worn seals nor get burnt off as quickly and YES I'd feel a bit of sluggishness after making the change. That said, there is not a very big difference between 5w-30 and 5w-20 where I would think you could feel the difference - which is why I say if you have a NON-MDS Hemi it'd be no big deal...

 

nah. you'd never be able to tell any difference. There's probably 1/2hp at the rear wheels lost from the difference. Basically unmeasurable!

MDS could potentially be effected though. I know my dealer seen a code for incorrect oil type with me using 5w-30 but he didn't think it was anything of concern. They claim MDS is very specific and I have my MDS disabled so I wouldn't know.

 

Your first problem wasn't with the oil change, it was who you took it to to change the oil. I wouldn't let those idiots at Pep Boys put air in my tires let alone touch my motor.

 

Strictly parts at Pep Boys. I ended up flying to AZ from NY because my father-in-law took his 2000 Jeep GC (4.0 I-6) there because of a coolant leak. They quoted him well over $700 for radiator, water pump, coolant, labor, etc. I told him it would be cheaper for me to fly out and fix it for him. So he flew me out. Turned out to only be the water pump. $35 part plus permatex plus $350 plane ticket. Much cheaper and done right.

 

Do a Google search for Pep Boy problems or better yet law suits. You'll be able to read for hours and it'll scare you to NEVER let them touch your vehicle again...

 

hahaha... I wont be going back because of previous problems I had with them. Problem is, I don't know of a trustworthy mechanic around here. I have a manual for my truck (haynes) but still... I wanted to change my spark plugs because they've never been changed at all and I called the dealer. The dealer wants $301 to change the spark plugs. Insane for some cheap parts! I will be looking for someone to do this for me. They said the price was so high because it's a part of some "tune up" and they wont JUST change the spark plugs... The truck was handed down to me from someone else and my mother would rather I not do the job myself (as silly as this sounds!! ). I've only recently been getting under the hood of my truck so it's understandable. I'm having the dealer JUST change the oil next week as it's about that time again though.

 

Plugs aren't terrible just time consuming on the Hemi and the back two can be tricky to get to. You should be able to do them yourself for under $32 and about two to two and a half hours of your time. Oil changes, I'm not trying to make you feel bad but my 12 year old niece can do an oil change by herself - and has...

 

What about if i use 0-20 instead of 5-20 on MDS engine ?