Hi- new (old) 4runner owner here. 2002 SR5 with 114K miles.

I've read the posts about dangers of switching to synthetic in high mileage engines causing (uncovering) leaks. I have no idea how my truck was maintained except I found a dealer oil change sticker, so I'm presuming conventional oil changes over its life, not knowing how often they were done.

Am a synthetic guy at heart and really want to switch to Mobil 1, but want to hear others' experiences who may have made the switch at high mileage and what the results were (leaks? no leaks?)

Thanks!

Here's the problem; if only petro oil was used and the changes were stretched out beyond the recommended intervals, sludge could have coated the inside of the engine. The sludge could have coated the seals in the engine. When you start using synthetic oil (which has very aggressive detergents), the sludge that was sealing gaskets will now leak. Also the oil filter will collect the sludge and will need to be changed very frequently until the engine is clean.

This is not a guarantee but you can pull a valve cover to get an idea if there is sludge buildup.

If you do not know what type of oil was used and/or if it was changed at the recommended intervals I suggest you just use dino oil and just change it at the OEM recommended intervals. Trust me when I say; if you use synthetic and have these issues you WILL regret using it. It is not worth the troubles you will experience.

Koz

Thanks for the balanced reply, Koz. Makes sense- I think I'll just proceed with Castrol dino 5w-30 and leave it at that. Altho the thought of the possibility of removing possible sludge does sound appealing

I will say this motor is whisper silent- timing belt and water pump were done 10k miles ago per the sticker on the cover. There is no hint of ticking or valve train noise at all, so I'm guessing the motor is in pretty good condition, overall. I think my first order of biz will be to put on an external transmission cooler that will eliminate milkshake risk... the thing that killed my Pilot with 55K miles on the clock.

I used to ran Castrol through mine..

but now, I'm running Mobil 1 through it and I'm almost at 225k..

I have zero leaks after I changed from Castrol to Mobil..

how often do you change your oil?

225k? Nice!

Good to know.. at what mileage did you change over? At 225K or sometime before that?

If I do dino, i would change every 3k, but synthetic I would go at least 5k.

I believe around 180k I changed from Castrol to Mobil..

At Costco, sometimes they will mail a $10 dollars coupon off for 6 quarts of Mobil 1.

After the discount, is about $22 dollars for 6 quarts.. plus the filter $4 dollars..

especially in Winter where temperature drops below 0 degrees, is nice to know that your oil doesn't freeze like other oil does..

Cool. So, did you have to replace your oil filter rather quickly since the Mobil1 probably cleaned whatever sludge was lurking in your engine?

114K ? Barely broken in man IF your worried you could always send your dino in for a oil analysis to see what it says before switching . You have NO worries with that amount of mileage . Hell , I switched my Prelude at around 310K , no issues .

nope.

I stuck with an oem toyota filter and I've been changing it around the 5k area..

I started running M1 at 115k (currently sitting at 125k), and no "sludge-reduction" based leaks so far. I did have an incident where the o-ring on my filter didn't seat properly -causing a minor leak, but that was an oversight on my end.

I think, that if you "create" a leak by running full-syn, then thats something that will take a bit of time to develop. Like, a few or more oil changes. I don't htink you'll see something like that occur within the first full syn oil change.

(Granted, ymmv!)

Thanks for the additional replies, guys. I think I've got enough confidence now to make the switch to M1

I would suggest pulling a valve cover to see if there is any sludge build-up before switching.

Koz

Good suggestion. Anyone know what the torque specs of the valve cover bolts are off hand?

Switched 4 trucks over to M1 at 100k plus and not a single problem yet