Is it necessary to use "marine grade oil" on oil changes? I have an Indmar engine and the manual says to use 15-40w Pennzoil Marine Oil. Wanted to find out if automotive oil will work just as well or marine grade oil actually will protect and extend the life of your engine.

I always use Delo 400 and Napa Gold oil filters, has all the specs as the Penzoil marine at 1/3 the price. An oil meeting the strict specs for hard working diesel engines will be fine for marine use. Your owners manual for the engine will tell you what specs the oil must meet.

i heard that marine oil has a special blend for marine engines, moisture!

The package is different. I use either NAPA Gold synthetic or Penzoil Platinum, which ever is cheaper. They are identical oils. NAPA Gold filter. Meets marine bursting specs.

Just got an email back from Indmar, they said I could use automotive Pennzoil 15-40w or Shell Rotella 15-40w without voiding the engine warranty.

If you use NAPA stuff you may also be able to find other places cheaper. Napa doesn't make anything. They are just like AC Delco now. They are nothing more than a name. They rebox everything. For example Napa filters are all Wix Brand filters. We carry the actual Wix boxed line and Napa just drops off the first digit. If you use a Napa oil filter of 1060 that is a 51060 in Wix. <BR> <BR>My brother who went to a mechanic school also said Penzoil is the one oil he wouldn't use. Supposedly it has some plastic in it that is suppose to clean but it actually justs leaves a residue in the engine. He seems to think Castrol and Mobile 1 are a lot better.

delo for me

Brett, I think what your brother is referring to is Paraffin wax and not plastic. From what I understand they have removed the wax but have never been able to confirm that. I know in years past you could tell a motor that had run Pennzoil during a teardown by the wax in the oil passages. Rotella is good oil. So is Delo just have to watch out for that warranty thing. So while you’re motor is under warranty use Pennzoil or Rotella and after warranty use whatever you want. I know I still use the Mercury synthetic oil because that is the only oil that they recommend until my warranty is up than I will probably switch to Mobil 1.

You're probably right Brandon. I changed a cam shaft in my 78 RS Camaro at 55K miles. I had put nothing but Kendall oil in it. The rocker arms and everything else had a thick layer of paraffin wax on it. I have tried to avoid oils containing paraffin ever since.

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Castrol...castrol.