Two great oils and excellent prices!!!
 

Castrol makes a great "newer" fully synthetic 20w-50 for about $6.50/qt and an excellent 20W-50 semi-syn for $4.25/qt. As Merc went to semi-syn this would be a no brainer.

As you know V-twin is up to around $10/qt and gold cap
$9/qt...you decide! (V-twin is still king kong and worth the money if $$ is not a problem as it is a Grp V. PAO)!

Most synthetics are now Grp III. and were previosly grp IV. or V. PAO's.

Grp III.s' have been imroved and meet the former grp IV. specs with elastomer additives put into the base to reduce shearing (ie. Goldcap).


I am now using Castrol or Valvoline Fully Syn ($6.25/qt) with excellent results from oil analysis samples sent and would have no problems using the Castrol Semi syn 20w-50 as well ($4.25/qt) (it is very close to a Grp III. fully syn I am told) with 40 hour changes.

(My change over is mostly due to what I consider overpricing of some of the other brands for what you are really getting in the bottle.)

I can still buy red cap 15W50 Mobil 1 for $23 for a 5 quart jug at Wally World.

How does the Castrol compair to the Merc semi syn? Might be in one of your older threads but I'm to lazy to do any digging. :D

I never ran an analysis with the Merc Semi syn but labeling suggests comparible.

Royal Purple :boat: