Premium vs. Regular and the catalytic converter?

[rickbaier]

I own a “California” 94 E-320 wagon. The owner’s manual indicates that running less than a premium grade would clog/damage the catalytic converter. Does any body know if there is any truth to this? If no, has anybody noticed a significant difference in gas mileage when using regular over Premium. There was a .30 cent difference at our local gas station today. Running regular could save me (us all) some bucks..

[hamada128]

It would save you only $4.50 per full tank.

[Defiant]

Cataclysmic diverters only care about lead in the gasoline's makeup. So long as it's unleaded, the octane rating won't matter a whit.

['91 300CE]

I will tell you from experience... my 300CE had regular run through it its entire life as near as I and my indy could tell and the cats were fried because of it... and the engine was a mess, the emissions were never right on it.

I will never put anything less than premium in my car... why? Because the engineers say not to.

If you are concerned about fuel prices... drive a Honda and put the Merc. in the garage or sell it.

[roycehof]

I once stopped at a gas station that was out of super (and subsequently mid-grade) and I put in regular. The car ran very poorly. I believe that a "knock" sensor becomes enabled and that retards the timing making the car run rich. The rich mixture would damage the catalytic converter. By the way, my mileage was terrrible also. As soon as I was down to half a tank, I filled up with super and after a brief while the car returned to normal. My car is 94 E320 so I imagine yours is the same set-up. The money you think you are saving will be wasted with the terrible mileage (due to the car sensing the detonantion of the low octane fuel and retarding the timing). Learn by my mishap - DON'T DO IT. In my case I was low on fuel so I was stuck, but next time I will out in just enought to get to the next station. It really ran poorly - No zip at all.

[omairtheman1]

premium fan... never had anything less in any of my car... you win in the long run!

[neanderthal]

some of you are posting doo doo.

the knock sensors are only available on the M104 engined 124s. the M103 engined ones do not have knock sensors.

if they detect pinging they pull the timing. so your whole the fuel burned my cat tripe is just that, tripe.


as stated already, the cats will get fried if you use leaded fuel.
if your cats are gone with unleaded then you have another unresolved problem that changing fuel octane might hide, but not eliminate.

[rickbaier]

After reading the manual and your responses it makes sense to continue using premium (unleaded of course). The engine appears to be designed to run on higher octane fuel as indicated by the 10:1 compression. Also I understand pre ignition (“Pinging”) is often not audible and running regular can cause some serious long term problems without us even knowing about it. So I will stick with running premium and probably get better power and continue to sustain my 25MPG (actually saving money).
Thanks for all your advice

[Glide Ride]

While not worth it to me, a compromise is to buy 1/2 93 octane and 1/2 89 octane. This will give you 91 octane, which is what the manual calls for.

[RBYCC]

Originally Posted by neanderthal

some of you are posting doo doo.

the knock sensors are only available on the M104 engined 124s. the M103 engined ones do not have knock sensors.

if they detect pinging they pull the timing. so your whole the fuel burned my cat tripe is just that, tripe.


as stated already, the cats will get fried if you use leaded fuel.
if your cats are gone with unleaded then you have another unresolved problem that changing fuel octane might hide, but not eliminate.

Believe the OP vehicle is an E320, making it an M104-24V.

Unburned hydrocarbons can and will damage a converter as they will elevate the temp in the converter possibly causing a melt down....