That Age Old Synthetic Question

[BRUIN8124]

I have always run synthetic in my engines, differentials and T-cases...

I have a new to me 03 4Runner Sport 4WD V6 with 121K. I have no clue what kind of oil is in there. I also have no clue when the diffs and T-case were last changed.

Is it too late/too old to switch to synthetic oils in the engine, both differentials and the T-case?

I understand that synthetic oil does NOT cause leaks, bad seals do. However, I do not want to switch then have my rig leaking like a sieve everywhere I go. I pretty much cant afford to replace all those seals which are not leaking at this point in time if they decide to start.

Should I leave well enough alone or go for it?

 

[MikeInNH]

You can switch to synthetic and back without issues any time you want with no issues what-so-ever. If the seal leaked with syn oil it'll leak with regular dyno oil. Don't worry about it.

 

[97BlackAckCL]

I always use synthetic, always

 

[thzpcs]

Nowadays, there's literally no reason not to use synthetic, other than cost. New rubbers don't have the same swelling and shrinking issues, and pretty much every modern car is designed for synthetic nowadays.

 

[BlueHenT4R]

I just bought my '06 V6 with 104k mikes in December. I checked Toyota owners site and original owner had TGMO put in on schedule since new. I immediately put in M1 EP and M1 75w90 in all diffs/xcase and have put 11k miles on since.

No leaks.

Go synth and don't look back.

 

[Jerm]

Bought mine with 112K immediately put synthetic in everything no leaks all is well.

 

[BRUIN8124]

Awesome! Thank you all. I now have Mobil 1 in my engine and I feel better already...

I will do both diffs and the t-case once my driveway isn't such a mud hole haha.

 

[daka320]

Bought our 04 4runner in 2010 with 80k on it. Changed everything to synthetic. Been doing oil changes every 5k and all the others every 30k. 186k on the odometer now with no leaks or problems.