what oil to use?

[bud37]

I have considered using the 25w40 marine oil for a couple reasons.
The first is the cold number and the hot number are closer together. In my opinion in a boat engine that already has a cold thermostat and perhaps an oil cooler, the engine oil will take a while to get hot enough to trigger the change to acting like a 40 wt oil. This could be a real problem if you beat on it too soon after start up.
The second reason is where can you readily/easily get good SAE 30 and 40 wt. anymore.

Now ….in my mercury engine manual it clearly states the oil choices, 25w40 first, then SAE 30 or 40 depending on ambient for start up….then it states not to use synthetic oil or multigrade. This is a 2001 mercruiser mx6.2 GM engine.

As for the ever-present debate about the cost of oil….IMO there is just far too much smoke and mirrors involved in marketing, so it is very difficult to pick thru it to make a decision as to what is a valid reason to purchase or just another hand in your pocket. Show me some real research data and oil analysis numbers.

All that and I still consider the right oil to be very important and have always bought what I believed to be the best at the time not based on price. Buy what your manual states, even though sometimes it seems to be quite arbitrary.

[Craig_B]

I know this vid shows a different viscosity but I find this guys channel to be be very informative and entertaining.

A good comparison between Mobil 1 and Rotella.

[url]. https://youtu.be/hTyrc1zjKEA[/url]

[RGrew176]

In each of my Bayliners I only used the Mercruiser oil. Never had any issues.

[Tireless]

The Rotella I use is not the one as depicted. I use the 15W40 Rotella, (T4).

Not sure I would go to a synthetic blend. I was advised against using a synthetic blend oil, especially in older engines. Maybe someone that is more knowledgable than I can chime in, I would also like to know.

Greg

[waybomb]

Original synthetic is not the same as current synthetic. I use M1 in my cars and generally get about 18,000 miles between changes based on the cars' service interval indicator. Last car I sold had 356,000 miles ont hat engine, changing it every 18,000 or so,

But then again, I won't use a synthetic in my old engines. I do not have roller lifters; they flat hydraulic lifters.

I use Rotella-T (for diesel engines) in my Crusaders, and then I add a can of GM EOS. The original stuff in the cardboard or metal can. I buy it whenever I see it; it has a very high ZDDP content. The newer EOS in plastic containers has reduced ZDDP.

I do the same with my drag boat which has high spring pressure flat mechanical lifters. Haven't wiped a cam yet.

PV has rollers, and 16 quarts of oil in each engine, so those get two cans of EOS when the oil is changed. When I bought PV, it had flat mechanical lifters and regular oil. I wiped all three cams. First rebuild used same grind cams and new flat mechanical lifters, went to Rotella-T and 2 cans of EOS. When I pulled them for a refresh, I went to rollers, but the cams and lifters were in beautiful condition.

[Midnightsun]

It's more important to change oil on a regular basis than choosing a particular brand IMHO. Never seen or heard of any case where someone used brand X and had issues. Rotella is well documented being used for decades in several application and as widely used/recommended as Mobil 1 so it cannot be bad oil.

Marketing hype is rampant not to mention very deceiving. I happen to run a business and see this day in and day out. I can count on 1 hand all the truthful salesman/reps I have seen in over 40 years.

One thing I hate is these 20,000km oil changes on my Mercedes AMG, just asking for trouble in the long run if you ask me. Just makes me feel like I am neglecting something. Good thing is I keep my cars for about 3 years and then give the problem to someone else to worry about.

[waybomb]

Hans
I tend to keep cars until they are no more. My E430 is the one that I sold at 356,000 miles. This was a few years ago; I still see that rust bucket running around town and no smoke out the pipe. Man, that water based eco-paint surely sucked. You can trust the service intervals. Whatever algorithm they use for determining changes works.

[Craig_B]

Not going to comment on boat engines but I can tell you in automotive applications I would never recommend following the onboard oil change monitors. They are always inaccurate. As someone earlier stated changed your oil frequently and on time. Conventional oil every 5000 km. With 30 years on the bench I can tell you since the on board oil monitors arrived there has been an huge increase in engine failure due to lack of lubrication, sludge etc.

Replaced many engines on 1970s and early 1980s vehicles.
Hardly ever changed an engine on 1990s + vehicles but when those onboard monitors came around started doing more engines than ever before.

Oil isn't that expensive. Buy a good oil and change it every 5000 km.

[denpooch]

I use 15W40 non synthetic per Crusader engine manufacturer. Here is what the engine manual states about synthetics:
"...Synthetic engine oils are not recommended for use in Crusader Marine Engines. Synthetics may offer advantages in cold temperature pumpability and high temperature oxidation-resistance. However, synthetic oils have not proven to provide operational or economic benefits over conventional petroleum-based oils in Crusader Marine Engines. Their use does not permit the extension of oil change intervals.."
On another note....
Viper you delineate the difference between 'automotive' and 'marine' oil. I never knew there was one. I have never noticed labeling on oil stating 'For Marine Use'. As I am using 15W40 per Crusader, does it matter if I purchase WEST MARINE 15W40 (we assume that is for boating applications) or ROTELLA 15W40? Isn't 15W40 - 15W40??

[Viper]

I'm not familiar with WM oil so I can't comment, but no, not all 15W40 oil is the same, I think we can all agree on that much. As for the Rottela, I used to be okay with it in marine gasoline engines but I really am on the fence now and wondering whether it is the best fit for reasons I posted earlier. To be safe, I'll use it for diesels only. If you're looking at a Crusader manual from the early 2000's you should contact them and ask about their thoughts now. Oils have changed since then and engine OEMs are always slow to catch up with changing their recommendations unless there is a major hardware design change that requires a review of their required formulations. I think you'll find though that it's just easier and for liability reasons they'll just tell you to stick with the manual unless the person you talk to there really knows his stuff.