Synthetics are generally superior(but the gap has closed dramatically in the last few years), .....older vehicles you may see some seepage or leakage around seals.
This is what majority of folks advised me.
In that engine I would use a solid 10w40 if you can find it. Rotella synthetic 5w40 would be an excellent choice if you decide to use synthetic. But if you are just driving in the summer, the 15w40 diesel oil would probably work well for you, since all your startups will be above 10-15C...
Will using a synthetic diesel for winter & colder months (like 5w40..heard from many as good for cold starts when in NY temp goes way low like this winter), then changing to non synthetic diesel oil like Rotella 15 w 40 for warmer months will be a problem? or just stick to either non synthetic diesel all season or synthetic all season. Please advice?
You said that the Jeep is backfiring and running roughly. You did NOT mention that you had replaced the spark plugs, cap and rotor. If you still haven't I would most definitely do that as the first step.[/quote]
Thanks all for your support. Was at the mechanic today. Jeep runs fine now. They figured out it was due to intermittent flow of charge to distributor due to faulty wiring.
@ Kuato: I changed spark plugs ( many times as they got black in a few hours )distributor & cap,ignition coil and module since these symptoms started. But finding faulty wiring was beyond my skills. I doubted like the previous 2 mechanics on motor and module and weber carb.