Synthetic Oil - No Going Back??
 

I was talking to a friend the other day today about the idea of using synthetic oil in my diesel and how starting is supposed to be easier in cold weather. That is one of the pros, and one of the cons is the extra expense. Then he said he was told that once you switch to synthetic oil, it is not good to go back to regular oil. If this is true, it would nix the idea of using synthetic in the winter and regular in the summer.

Is there any truth to this?

There is no truth to it.

Switching between synthetic brands may indeed be bad, if they are made from different bases. However, all synthetics on the market are compatible with conventional oil.

Why is that Matt? (honest question...not trying to be a smart ass)

It's what the manufacturers claim. I do not know the chemistry behind it.

perhaps it's to scare you into brand loyalty...

I'm asking because I've gone back and forth between Delvac 1 and Redline a couple of times already... I'm currently using Delvac 1.

My father used to switch his cars over to dino oil in the summer after they got higher miles on them (300mile commute). Never had a problem. Buy good oil, that's all.

They are definitely compatible. I'm going back to conventional oil as soon as the weather warms up again. Mobile 1 has served me well with cleaning out the passages for the cam bearings, but it tends to find its way thru mated surfaces of older engines such as my '77 M110. Back then, engines weren't made with today's closer tolerances. If you do switch back, I suggest letting the oil drain over night to get as much out as possible. This is, of course, starting at operating temp.

hell, If you make it 300K on dino then you must be doing something right, so don't switch to synthetic. Thats how I look at it.

I switched to syn oil. seems like a fairly modest amount of cash compared to the overall money spent on the car.

I have been putting crap Autozoo Coastal junk dino in my SDL for winter storage...never had a problem. Come spring I drain it and refill with Amsoil or Mobil Delvac 1.

I do it for $$$$$. Synthetic oil costs me about $50 for a change, cheap dino is $20. Since the car is just sitting, the oil doesn't really matter. I put maybe 5 miles on the dino oil every spring, between moving the car out of the garage, and taking it for a ride.

Switch to synthetic, no matter how many miles it has.

Once you pick an oil, you should stick with it.

rotella synthetic ftw+

There is some truth to it. Back in the 70's when synthetics first became commercially available, they wouldn't mix with conventional oils. I don't know if or how the engine needed to be flushed. I do remember that you couldn't mix in a quart or two of conventional oil. In the early 80's, this changed. I have switched back a forth a few time, with no noticable effects. The car has 210K on it. I have switched between brands too. Castrol, Mobil 1, Shaffer (blend) and Pennzoil.
Tom

A lot of oil used to be sold as a blend - that is, a blend of dino and syn. You can switch back and forth between the two without any cause for alarm.