Gasoline Grade: Which Should I Use in My VW Van?

Gasoline is rated by its octane level. The higher the octane, the more stable the fuel is, and the less likely it is to prematurely ignite and cause the engine to “knock,” which usually results in a pinging sound. This can lead to catastrophic engine failure in a surprisingly short amount of time, with very little notice. Pre-ignition can occur in a particular engine design for various reasons. For whatever reason it occurs, high octane fuel can prevent it from happening.
Higher performance engines typically have higher compression ratios (CR) and are more susceptible to knocking than lower CR engines. Those of us who grew up in the '60s and '70s are accustomed to this reality, and as a matter of course listened for pinging whenever driving a vehicle with a high performance engine. Pinging occurs only at high power demand (high load). That is, if you are just cruising down the road, rarely if ever using full throttle, and don’t need all of the power the engine is capable of producingpinging does not occur. "Old-schoolers" like me know when to listen. To this day, on long trips in my Bus or Vanagon, I ALWAYS listen for pinging after each tank fill-up. I simply turn down the radio, roll down the window, and listen. If the engine is going to ping, it will do so on a long grade at above 80% throttle-especially at altitudes under 3000 feet. If I got a tank of bad gas, I know that for at least that tank of fuel, I gotta keep my foot off of it, and stay below 80% throttle. This happens a lot in Mexico.

In the late 1980s, Bosch came up with a “knock sensor” feature, whereby the engine management system senses knocking and automatically makes adjustments to timing and/or fuel delivery and/or valve timing so the knocking stops. The result is that the engine simply produces less power in exchange for staying in one piece. It is realy no different than what us old-schoolers have been doing all along, except it is done automatically for you by a device that does not have to turn the radio down or roll down the window, or even stop to eat or pee.
Eurovans: Having been designed in the late '80s, all Eurovans are equipped with a knock sensor system. You can run low octane in a Eurovan, and the engine will adjust if knocking occurs. So, it makes no difference what grade fuel you are usingthe engine management system will make the necessary adjustment. If you need more powerif you plan on towing, for example you should buy the higher octane fuel. The bottom line, though, is that neither is likely to hurt the engine.
VW Buses and Vanagons:  By contrast, Buses and Vanagons were designed in the '60s and '70s and DO NOT HAVE knock sensing capability. That is, if you decide to use low-grade fuel, or end up with some bad gas by mistake, the engine has no way of adapting to it. The little engine will try to push that big box around with all its might, knocking or not, until it pukes. And unlike the newer Eurovans—with their larger, more sturdy engines—the engine in a Bus or Vanagon is BARELY able to push it down the road even under ideal circumstances. Anyone who has spent any time behind the wheel of one of these vehicles, even one fitted with a GoWesty high performance 2.5 liter engine, finds themselves trying to push the accelerator pedal through the floor without realizing it. So: Always run premium in any Bus or Vanagon, or you will risk destroying the engine. And even with known good fuel, it is a good idea to experiment a little, learn what pinging sounds like, and make changes in your driving habbits as needed to avoid it from happening.
What about the cost? Well, at $3-5 per gallon, what is another twenty cents? A lot less than another engine, that’s for sure.

What about MPG? Don’t you get better MPG with higher octane fuel? Baloney! Don’t believe it! It is just not true. You can run regular in any Eurovan without hurting it and get the same MPG.

What about running hotter? Doesn’t my engine run at a HIGHER temperature with HIGHER octane gasoline? Baloney! Don’t believe it! It is just not true.