At 02:23 PM 5/15/2015, PB wrote:
>About a year and a half ago there was a thread about which gasoline to
>use.  If I remember right, there was a general consensus that Vanagons were
>made to use cheap gas,

Stop right there, please.  If we think in cheap 
vs expensive it all gets very confusing.  After 
you figure out what sort of gas you want to use 
then you can try to find it cheaply.

The Vanagon requires fuel with a certain octane 
rating to operate correctly.  Octane rating is a 
number that rates the gasoline's ability to 
resist exploding inside your engine.  You don't 
want it to explode.  You want it to burn rapidly 
but smoothly, and for the Vanagon at sea level 
you need to use fuel with octane rating of at 
least 87, American style.  Butbutbut, you 
say.  There are two common methods for rating 
octane, called the Research method and the Motor 
method.  In Europe they like the Research method, 
and the Vanagon needs gas with a Research Octane 
Number of 91, just like it says on your sticker 
(you can see the RON if you look).  In the US for 
some reason we like both methods.  We like them 
so well that we use the average of the two for 
the octne number we stick on th epump.  And that 
number is 87, regular grade fuel.  If you're 
really flogging the beast the owner's manual says 
you can use higher octane (mid-grade) if you want, just in case.

If you go up in the mountains you'll get another 
scare because the pumps will say 85 on them -- 
that's ok, because of the altitude 85 octane is 
sufficient.  Note that "high-octane" gas isn't 
filled with more energy than regular -- it's 
actually filled with a bit less.  Its virtue is 
burning smoothly in high-compression engines that 
tend to make the fuel explode.  Its other virtue 
is that in order to encourage you to buy  the 
fancy gasoline, the blender/refiner/brand may put 
lots of lovely detergent and ssuch in their 
high-test, but skimp on it in their regular 
grade.  If that were true, either using Techron 
from time to time or switching to the expensive 
gas would keep your engine from getting all crudded up internally.

And that brings us to Top Tier gasoline.  Some 
brands have agreed to sell only gasoline with a 
superior detergent package and other good 
qualities, and in turn VW and other mfrs suggest 
that you buy this high-quality gas carried by the 
Top Tier brands.  It comes in high, mid, and low 
octane, but they all have the good detergent 
package.  VW thinks it's a very good idea for you 
to use gas meeting the Top Tier standard as it 
will keep your engine clean and happy 
inside.  But they don't care which brand you use, 
and they don't forbid you to use gas that is not 
Top Tier.  They just warn that you may not like 
the long-term results when your engine 
potentially gets all clogged up with stuff.

Yours,
David

>  so I immediately switched from 91 octane Costco gas
><http://blog.modbargains.com/what-is-top-tier-gas-and-why-it-matters-its-at-costco/>
>to 87.
>
>A few weeks ago, after a tuneup and compression
>​ adjustment​
>in all 4 cylinders, my mechanic, Bela, told me I was using "BAD GAS."  He
>told me that Costco gas was BAD, and would ruin the cylinders, and that I
>needed to use 91 (89 at the lowest) octane *MOBIL* gas for the best
>performance.  (Mobil gas is extremely high-priced, and averages $.3
>​5
>  - $1.00 per gallon above all other brands.)  OK.  So I switched to Mobil
>91 octane - for my van ONLY, and I actually have been getting better
>mileage.  (Had to use Gas Buddy to find the lowest priced Mobil, which is
>​
>on my daily route, and pay cash to avoid credit card surcharge
>​.)​
>
>
>Yesterday, I noticed the dog-eared stickers on my passenger door, and was
>able to see that 91 octane was recommended when the vehicle was made