Recently did an Oil Change from Conventional 5W-30 to Synthetic 0W-40 Oil, Concern?

[arjun90]

A week ago I performed my own oil change. It was a pretty simple process after gathering all the appropriate tools. Prior to my recent oil change, the car has always gotten its oil change every 3,000 miles using the conventional Castrol GTX 5W-30 oil and third-party German-made Oil Filters. The last conventional oil change was done in October, 2014 at around 137,000 miles. The owners manual encourages car owners to use synthetic oil but is not necessarily a requirement. However, whether you're using conventional or synthetic oil, the car only works with either 5W-30 or 5W-40 as per the owner's manual. No where in the manual does it state the car uses 0W-40. I changed the oil myself last week at 141,900 miles and installed a Genuine Audi Oil Filter and Mobile-1 0W-40 Synthetic Oil (purchased '2' 5-quart containers from Walmart, to meet the 6.9 quart capacity). The car is performing fine for now, but do I need to be concerned in the long run? Should I redo the oil change and use 5W-40 or 5W-30 synthetic? The mechanic who used to work with the previous owner, mentioned that changing oil grades and changing from conventional to synthetic oil can be harmful to the lifespan of the engine and end up in costly damage; is this really a fact?

Please let me know. Thanks again.

Current:
Audi A6 (C5) Avant, 2004 (3.0T, Quattro)

[G0to60]

You should be fine. The only real issue of changing from conventional to synthetic is that engine seals and gaskets can start to slightly leak due to the cleaners in the synthetic oil. This is usually only the case in much older cars where tolerances weren't as tight. As far as the grade, you are just fine with the 0w-40. That is what I have used (Mobil 1 synthetic) since ~150,000 miles and I'm up to just over 200,000 miles with no engine issues.

[Milehi]

Should be ok, as goto60 stated you may see some oil usage. Worst case, if there is any sludge build up in the engine the synthetic WILL wash it out of it's hiding places and deposit it in the oil pan and journeys and anywhere else the pump can pump it until the pump stops up. If you get an oil light, believe what it's telling you....

[arjun90]

Thank you all for your feedback. The car I'm driving is ~142,000 miles,

What about the residual oil that stays behind when doing the oil change. Should I be concerned about the minute amount of conventional 5W-30 oil that is still circulating in the engine? There's always some of the older oil that stays in the oil pan in between oil changes.

[G0to60]

Thank you all for your feedback. The car I'm driving is ~142,000 miles,

What about the residual oil that stays behind when doing the oil change. Should I be concerned about the minute amount of conventional 5W-30 oil that is still circulating in the engine? There's always some of the older oil that stays in the oil pan in between oil changes.

You don't need to worry about the residual oil that is left behind. It will all mix together and you, or the engine, won't notice a thing.

[noob5]

OP,
you will be fine with synthetic 0w40. I use Mobil 1 0w40 on all my cars without issue.
Btw, did you add forced induction to your car or did you swap in a 3.0T?
I'm guessing you added a supercharger since your engine has ~142K miles.
Or maybe typo?

[arjun90]

The car was regularly serviced every 3,000 miles with conventional 5W-30 Castrol Motor Oil. A member of the family made me the next owner when the car was at 132,000 miles. It's a Audi A6 (C5) Avant, 2004 (3.0T, Quattro) model. These are designed to last long as long as it is properly and regularly serviced. Pretty comfortable with the Audi, best 4-wheel drive system out there as well as the best body materials; very confident in terms of drivability and safety.

[julex]

The car was regularly serviced every 3,000 miles with conventional 5W-30 Castrol Motor Oil. A member of the family made me the next owner when the car was at 132,000 miles. It's a Audi A6 (C5) Avant, 2004 (3.0T, Quattro) model. These are designed to last long as long as it is properly and regularly serviced. Pretty comfortable with the Audi, best 4-wheel drive system out there as well as the best body materials; very confident in terms of drivability and safety.

2004 3.0 is NOT turbo, it is just NA 3.0. 3.0 engines are known to be a problem prone engine with cam lobes wear issues.... the fact that it run dino oil all its life is a big time red flag especially on this engine.

Who runs dino oil on engine that specifies and requires synthetic oil with specific formulation to prevent engine wear?!

What these engines are good for it to become a 3.0 crankshaft donors for 2.7t high HP/TQ builds.

[arjun90]

This post made my day, so true!

I would like to ask the previous owner the same, lol. The owners manual is so clear when it states to use synthetic oil. Being the next owner of this vehicle, I'm running synthetic from now on, no exceptions.

2004 3.0 is NOT turbo, it is just NA 3.0. 3.0 engines are known to be a problem prone engine with cam lobes wear issues.... the fact that it run dino oil all its life is a big time red flag especially on this engine.

Who runs dino oil on engine that specifies and requires synthetic oil with specific formulation to prevent engine wear?!

What these engines are good for it to become a 3.0 crankshaft donors for 2.7t high HP/TQ builds.

[julex]

This post made my day, so true!

I would like to ask the previous owner the same, lol. The owners manual is so clear when it states to use synthetic oil. Being the next owner of this vehicle, I'm running synthetic from now on, no exceptions.

Especially that Walmart has at least three oils (for dirt chep) that fill the bill here:

Mobil 1 0w40 European Formula (VW 502 approved)
Shell Castrol Syntec with FST in 5W40 (VW 502 approved)
Shell Rotella T6 (not approved but proven to do well in our engines) in 5w40