I'm with you. Gasoline is like mouthwash. It all comes from the same spigot at the plant/refinery and goes to different retailers with different names.
In so much as combustion chamber deposits, other than some carbon on the piston crowns and a little varnish above the ring lands, so what.
Flip,
Exacatackly. You would prolly know best on how much build -up can occur seeings how you rack up 100's of thousands of miles. But then Diesel is a different aminal all together....
Actually, diesels stay pretty clean in the combustion chamber as the heat factor is higher than a 4 cycle gasoline engine. You get a little carbon on the crown and a carbon ridge at the firewall and that's about it. 24-28 to 1 does a lot better job of burning off accululating junk than 7-10 to 1, plus the new ULSD diesel is almost devoid of soot causing additives.
If you pulled the head on your JD, you'd be amazed how clean it is.
Just as an aside I run mine on 98 Octane - cos I live in Oz and we get 93 - 98 at the pump.
I recently changed the mapping with TuneBoy but it has always (and still does) run as smooth as silk. I used to get the popping on decel, but thats gone now as well.