Switching to synthetic at 93k...good or bad?

If you have any marginal gaskets and seals that are sealing because they have gunk on them, the synthetic oil will clean out the gunk around the seals and find the holes in them.

My rear main seal on my Dakota started to leak with synthetic oil when I switched at 40K miles. I switched back, the leak stopped. No harm done.

 

I switched my '97 Tacoma 2.4 4 cyl from Castrol GTX 5w-30 to Syntec 5w-30 at 140k miles. At that time I quit the 3k mile oil changes and went to 10k mile intervals. Truck now has 335,000 miles and runs great. Never opened the engine once. Gave to my son last year when I bought a new Tacoma. I swapped it to synthetic at 2,500 miles. Using Mobil 1 EP 5w-30. Still doing oil changes at 10k intervals. I change filter every 5k miles.(Toyota filters). I did use Fram on the '97 Tacoma. I need to get an oil analysisdone the EP on this oil stands for extended performance. Supposed to be good for 15k miles. From what I've read, oil doesn't go bad. It's that additives that breakdown overtime. That would be awsome to change the oil just every 15k. With that said, all my driving is highway miles. Not stop and go. If you do mostly city driving I wouldn't go that many miles between changes. It really isn't the miles on the you drive. It's the hours on the motor. An hour in the city you may only drive 15 miles. On the highway you may drive 70 miles. I wish they would convert to hours over miles. This how they do it for machinery.

 

Good point on the filter change at 5k.

 

Only thing bad would be waiting til 7k miles, I did my older cars every 5k, now on the truck ill do the same

 

X2

I run a full synthetic but change my toyota oil filter every 3,000 miles and oil every 6,000.