Hey guys. Just got a 1998 Cherokee with 195k miles. No rust, very clean interior, 3 years and about $7k worth (all shop performed) of maintenance records. 15x8 -19mm Ultra wheels, 31 in tires with unknown lift (3 in?). Questions/known issues:
- PO used conventional oil. I've never owned a car with this many miles on conventional oil. Should I switch to full synthetic? Also wanting to run some seafoam through the gas tank
- lots of oil residue around block and all over the underside, from the filter to the oil pan. I plan to replace valve cover gasket, filter adapter gasket, oil pan gasket and new drain plug. Ordered a rear main seal but unsure if it's worth replacing, but the oil pan will be off.
- wheel vibration at 55-65 mph. PO gave me a set of hubcentric rings that he thinks will fix it. Still doing research if that's the issue.
looking forward to wrenching and learning!

 

Welcome to Cherokeeforum

To answer your question, no you do not have to use synthetic oil at all.

 

Welcome. I wouldn't tear into anything oil leak wise until the valve cover gasket is replaced (with a Felpro blue one) and you have cleaned off the engine.

 

That would seem to be a good starting point - unless visible evidence suggests otherwise.

 

Use 15w40 diesel motor oil, that works best for me.

 

I've always used 15/40 &, from what I've learned from a few Youtube channels I follow would use a diesel oil - but there's no such thing in the UK now (except, possibly, from specialist suppliers) as all oil is marketed/packaged as being suitable for petrol (i.e. gas) & diesel engines. They still make the distinction in Europe, afaik, so might start getting my oil in France (my Citroen van runs on hypermarket own brand diesel oil, cheap &, somehow, seems appropriate) but major brand oil's expensive there.

 

I use diesel oil as well, Rotella T4 usually.