We're in Cordova, Alaska, and have just finished changing the engine oil. We've got 8 gallons of oil left aboard and decided to see what it would cost to add 5 additional gallons. We like to carry enough oil for a minimum of three changes - in case we should get water into an engine and need to flush it (it takes 2.5 gallons for a change).

There is a NAPA auto parts store next to the harbor where the fishermen buy parts, so we figured they were a good spot to check prices.

Chevron Delo 15-40, which is what we have been using, is $170 for 10 gallons. However, they have a NAPA brand oil that is just $120 for the same quantity. It carries the same government ratings as the more expensive Chevron brand. Is there a difference? We do not want to be taking chances with our little diesels!

So we decided to e-mail our favorite diesel mechanic, Craig Hatton (Hatton Marine in Seattle). We figured if anyone knew about oil quality it would be Craig. His main thrust is servicing fishing boats, and commercial fishing folk are notoriously tight with their maintenance budgets.

Craig's reply was, "When it comes to oil, I can only suggest using products from major oil companies - i e. Chevron, Shell, Exxon. It is good to remember that the SAE rating only reflects passing minimum government requirements and does not give a real basis to compare the quality ranges between products. Though these brands are more expensive, they are quality products and in the case of engine longevity and preservation I cannot suggest buying bargain brands."

Looks like we'll be staying with our higher priced lube oil.