Choosing proper oil


Please help me decide whether to change from “straight” mineral oil to synthetic blend oil for my car. If you can not help, please refer this to an appropriate person who will.

I own a 1991 Volkswagen Jetta GL diesel, which I bought used in 1996. I have used only mineral oil of a certain brand in my car. I buy my oil in cases of quarts. Recently, I learned that, in the brand I use, “straight” mineral oil is no longer available. Instead, I can get only synthetic blend oil.

I’m reluctant to change to synthetic blend. Tell me, please:

1. If I change to synthetic blend oil, what special measures I need to take.

2. If I change to synthetic blend oil, which viscosity I should use. Based on the owner’s manual, I use:

a. 10W-30 for Winter

b. 15W-40 for Summer

3. If I continue to use “straight” mineral oil, whether “off-brand” or “house-brand” is sufficient, as long as it is API service “CH.”

?Thanks! in advance for your time and interest.

Dave Stamm

Fort Wayne, IN

If you maintain weight and grade, I don’t know of any problem switching to a sythetic blend. I’d do that, rather than switch from a brand I’ve been happy with. But any good oil that meets weight and grade specs would work. Maybe just me, but I stick to name brands. You also might post this on a TDI forum, like, sure there are lots of TDI folks that have done this.

Here’s the oil discussion at TDIclub, which seems to say synthetic is specified…what does your manual say?

You VW requires:

5W40 (10W40 Acceptable) [15W40 is not a good idea.]

VW505.00 OR CF or higher

I get mine from Walmart Shell RotellaT

Make sure it meets the specs above.

Your 1991 is an IDI, not a TDI type diesel and if it has no turbocharger (you don’t mention it) is therefore not extremely particular about engine oil; but follow your owner’s manual if you can, using a diesel rated oil. If you can’t follow the owner’s manual, your suggested weights will be fine with either dino (mineral) or synthetic oil but make sure that you are using a diesel rated oil. 505.00 is not needed for an IDI diesel; is more expensive than you need.

I have been mixing oil brands and weights for years in my IDI diesel. In the summer, for example, I use two quarts of new 15W-40 diesel oil mixed with two quarts of old 10W-40 cc rated oil that I bought years ago plus one quart of new 10W-30 gasoline engine oil from a small stock that I want to use up. The three weights are also three different brands. My IDI engine has over 200k miles needs no oil added between changes. I have been mixing oil brands and weights for many years.

Your home site as an IDI VW diesel owner is, not

Use whatever grade and viscosity your owner’s manual specifies. You may switch to synthetic (and back) at any time. There are no precautions to take. Just use and drive as you normally would.

Got get some Rotella T synthetic 5w-40 from WallMart and forget the Euro-alph-numeric soup. The ACEA came into existence in 1991.

The 15w-40 is fine …it’s way more advanced than anything that existed when the Teutonic’s made your machine. Soot control is better than it ever was, and any 15w-40 or 5w-40 has a better HTHS than you require.

With an engine that old, you may consider using something like Auto-Rx (google it). It will decoke your rings and clean up any deposits you may have.