Hello all! New user here. I have always preferred Shell 91 (other brands 93 if available) for my Yamaha 600R.
If higher octane means extended life, I won't hesitate to spend a few more bucks.

Thanks,
Chippy

 

If the car does not require it (and Volvo's don't), no it does not. But I'm sure you'll find people who think it does.

The last time I tried to explain this, it got ugly. But have a read anyway:

Click here

 

Oh wow! I didn't know that question was that controversial!
My buddy's motorcycle with 87 octane had terrible gumming in the valve head. My 91 was clean as new. Maybe it's because of ethanol content, or age, or, oil leak or... who knows!?

My mechanic tells me that Shell has the least ethanol content, I take his word by faith!

 

It isn't necessarily controversial, it is just a lot of people don't know what octane is. Most people assume something that costs more is better. So they think 93 octane is cleaner or makes their car faster or increases their fuel economy, etc.

Ethanol content and octane are different. The pump will say how much ethanol may be in the fuel. Volvo has no problem with 10%.

 

What causes gumming in the manifolds/valvehead? Oil leak?

 

Leaking valve seals, a bad PCV system.

Can't speak for your 600R as to common causes.

 

Just noticed that my manual recommends 91, although 87 is acceptable.
I should have checked the manual before posting this rookie question!

Thanks for your advice!

 

I use 91+.

Waiting to long to change the oil will cause sludge.

 

Does engine oil degrade too over time?

 

Yes, oil degrades over time.

Waiting too long on oil changes causes it to sludge, but doesn't necessarily cause the valves to gum up (as there should not be any oil on them anyway). But don't do it anyway, it will cause a host of other problems.

The manual does recommend 91 but 87 will do no damage. I have almost 120,000 miles on my car using 87 octane, my valves are spotless. I pulled the fuel rail not too long ago it take a peek actually.