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"What oil weight should I use

"What oil weight should I use in a 1994 5.8FL OMC? 10W-40? Can I use synthetic? AMZOIL Marine, MOBIL-1? Recomend oil brands. What should I stay away from? Don't use regular car oils from auto stores right?"

Pretty sure OMC only ever reco

Pretty sure OMC only ever recommended using SAE30

You can use automotive crankca

You can use automotive crankcase oil. Use the viscosity recommended by the manufacturer.

"Since boats are run at higher

"Since boats are run at higher sustained RPM, get something that's rated for heavy duty use. That's what most companies are recommending now. Indmar recommends Pennzoil Marine but as long as it meets the spec codes, you'll be fine. Just keep it clean, use good filters (not Fram- they always get dumped on in tests for a variety of reasons) and don't cook it."

How about using Mercruiser 25W

How about using Mercruiser 25W-40 oil and a K&N High Capacity Filter? (Local Marine store recomended the oil and sold it to me)

"You can use that oil, but if

"You can use that oil, but if you noticed, the price is about the highest out there. If the oil used meets spec and is kept clean, you'll be fine.

By nature, any filter will present resistance to whatever is flowing through it. The only ways to flow more volume are by having larger orifices or larger surface area, assuming the orifices are the same size. You can cram more filter element into the can but at some point, it starts to work against you."

"Good ole Super Tech 30SAE is

"Good ole Super Tech 30SAE is all you need. Been using it for years and never have any problems. Wal-Mart doesn't have it's own oil refinery. Pennzoil just sticks a Super Tech label on their brand and makes it for Wally World. It's no different, meets all requirements. If you want added protection throw a can of STP oil treatment in there. Buying these sythethics and brand name oils are just a waste of money. I could see synthetics in a racing engine but for most boats its not needed."

"Bud- I don't know where y

"Bud- I don't know where you live but I'm in Milwaukee and when I changed to Valvoline Dura Blend, cold starts were immediately smoother, the oil stayed cleaner in the same interval and my mileage improved noticeably but I also didn't wait till the next change was due when I went to the semi-synthetic so it wasn't one of those "WOW- this is great stuff (after waiting till the oil looked like tar)" situations. I agree that cheap oil works fine in most situations, especially if it's kept clean and the motor doesn't overheat but boats are notoriously under-maintained and if you watch the posts on ANY marine forum, you'll notice that there are a lot of overheats in boats that are new, old and in-between. People also run their boats at higher sustained RPM than most cars and trucks. Besides, if a boat gets one oil change per year, it's not that much more money.

Read more of the threads and you'll see what I mean. Regular oil doesn't hold up well after an overheat and I suspect that a high percentage of boaters who do this, don't change their oil immediately after."

"Synthetics are thinner than p

"Synthetics are thinner than petroleum based oil so yes, easier starts are possibly noticeable at say 10 degrees Fahrenheit or below. As far as staying cleaner, I don't buy it. Synthetics get just as dirty and this is why it makes no sense to get synthetic oil and say "I change my oil every 10K because it's synthetic". The oil filter still needs to be changed every 3K regardless. Petroleum oils have been shown to last 5K-7K without breaking down. Of course synthetics are higher. I'm sure YOUR boat is not under-maintained so really YOU have no need for a synthetic. A marine engine should not be overheating but under those circumstances a synthetic won't break down and would be a good choice for someone who has no clue about boats and doesn't bother maintaining them. If spending more buys you piece of mind then that's fine. I just think a lot of people are wasting their money. I buy the cheapo oil because I know it made by a quality company. Super Tech has been made by Havoline and also by Pennzoil, do you think they stop the production line and say "oh this batch is for Wal-Mart, turn all the additives off and bring the crap out"? Nope, one goes in a black bottle and the Pennzoil goes in the yellow bottle. Super Tech now has its own full synthetic, hell it's probably made by Mobil."

"" As far as staying clean

"" As far as staying cleaner, I don't buy it."

You know what dirty oil looks like on a white paper towel and after wiping my hands, the regular oil was darker after the change, even though it was basically the same color as the synthetic when it was fresh.

I know a few people at GM's Desert Proving Grounds in Mesa, AZ and they agree about at least keeping the oil clean, but they have seen and done testing related to oil quality and run cars or trucks in destructive tests to see what they'll take, like using oil for a really long time with no filter change or draining the oil and seeing how long it lasts while driving the vehicle on their test track in stop/go and at highway speeds. The motors with synthetic did wear less and lasted longer after the oil was drained. The car with regular oil- they drove it for 250 miles before it finally seized.

I worked on boats for two dealers and you would be disgusted by some of the things I saw people do to tehir boats, then get mad because "My car never did this". 3 years between oil changes on a Malibu ski boat, the guy's kid tried to remove the filter and shredded it. I had to do three oil changes before the oil was actually clean and this was on a $45K boat. The oil was black, even after the first change, just from what was still in the motor. Other people- multiple overheats because they didn't read their manual and think that there could possibly be a bunch of weeds in their oil cooler.

Private labelling is nothing new- at least they use decent oil. Again, I agree that keeping it clean and cool is the best policy."

"Oil has another function exce

"Oil has another function except from the lubrication part and that is cooling. Almost 20% of the total engine cooling is done by the oil. The running temp of the oil may easily go up to around 120-130 Celsius. If severly overheated or poluted the viscosity goes up, the oil gets 'thicker' and does not circulate at the same speed, cooling ability goes down. Another thing to take into considderation is the life time of the additves. Unused there is no problem, but as soon as put into operation the lifetime is around 12 months. Quite similar to anti freeze which has about 24 months. It may lubricate in the way that the oil film is still there, but corrosion inhibitors, anti foaming, anti sludging (mud in the oil pan) etc may be gone. Change oil once a year if You want the engine to live, and change after 'extreeme conditions', like owerheats etc. The main difference between synthetic and normal oil is that the running hours in the 12 months periode may be extended somewhat. In general I would say that running hours up to 100 hrs/year 'normal oil' is sufficient on one yearly change, above that go for synthetic."