My understanding is that the molecular structure of synthetics make them more uniform and smaller, something that wouldn't necessarily be a benefit to WBX engines. Modern engines have tighter tolerances, which necessitate the uniformity and smaller size of synthetic oil molecules.

The only benefit that I can see to changing over to a synthetic might be a effective lubrication over a wider operating range (no, it won't really keep your engine significantly cooler). That being said, I ran 20W-50 Castrol dino oil in my WBX through Texas August heat with no ill effects, so I'm not sure how much wider an operating range regular folks need, unless they commute regularly in say, the Mojave desert. 

Now with the Zetec I'm running full synthetic, as that's what the Bostig folks (and I think Ford) recommend. 

I don't care so much that manufacturers require synthetic oils in their engines. What bothers me is when they use a proprietary oil specification. Keeping the '05 TDI Jetta using the correct oil under its warranty period was a major pain as a) I haven't lived closer than 50 miles to the closest dealership and b) the stuff is largely unavailable off the shelf and certainly isn't carried by any jiffy lube. Now I just use what I please. Fortunately, that was never a problem with the Vanagon.

-Jarrett

On Aug 16, 2012, at 2:49 PM, Dave Mcneely wrote:
> 
> I agree, no reason to switch to synthetic for a Vanagon, but lots of committed synthetic users around.
> 
> mcneely
> 
> ---- Don Hanson <dhanson928@GMAIL.COM> wrote:
>> 
>>  I don't
>> see changing over to full synthetic would make much difference on anything
>> except maybe a Bostig or a Subie powered one...
>