I don't own a Rangerover but have a boat with a 1996 Ford 302 Windsor V8 engine, the marine version of this engine is known as the OMC Cobra engine.

In 1996 the road version of this engine would have a roller cam setup and use 5W30 synthetic oil. The OMC Cobra version is almost identical but has a hydraulic flat tappet valvetrain, marinas advise the OMC Cobra marine version should use straight 30 grade mineral oil.

I suspect the straight 30 oil recommendation is due to OMC being slow to change their advice. They are certainly much slower to change their engine / mechanical designs than is the case for road going vehicle manufacturers. The marine version has been around since the earliest road going Ford 302's which came out in the 60's, I think a multigrade like 20/50 is better than the straight 30 oil. But my question was/is would a modern synthetic oil be better than a mineral multigrade?

It's normally not recommended to switch to an oil with high detergents after running a no detergent or low detergent oil because the detergent could dislodge old sludge and cause problems but I rebuilt this engine last year and there won't be any sludge in it... So on that basis I would prefer to run a modern multigrade that has detergent to help prevent sludge build up.

This is where my oil concerns might be similar to oil concerns of P38 owners... Unlike the road going 1996 engines my marine 1996 engine has those flat tappets, which ZDDP protects, but modern synthetics don't contain ZDDP while a mineral 20/50 will probably contain at least some ZDDP though most manufacturers don't tell you how much. Though a mineral 20/50 oil won't contain much detergent.

I've tried to research what's the best option for my relatively newly rebuilt 302 with flat tappets on boating forums, car forums, oil company discussion boards, etc, got a headache looking into it.. Most of the boaters stick to the recommended straight 30 but (as said above) I think that's just following old advice that ought to have been updated.

Today I had a chat with Opie Oils who recommended Valvoline VR1 20W50 mineral 'race' oil. They said that although it's a mineral oil it has better sheer strength (retains it's 20/50 grade) better than most synthetics, the 20/50 grade is a good match for the old straight 30 grade, it has a lot of modern additives / detergents and has high levels of ZDDP. I bought 2 x 5L containers of the stuff from their online shop.

I'm not usually so anal / picky about choice of oil, for a car I'll usually just stick in whatever meets the manufacturer's recommended grade, choose a well known brand and not worry about it. But when you believe manuafacturer advice is 50 years out of date because newer / better oils have come along while they haven't moved with the times and your situation is a bit more unique because you don't need to worry about dragging up sludge in a newly rebuilt engine, it gets you thinking or at least it does me.

What oils do you run in your P38's and why?

I use 15W-40 semi synthetic in my boat engine but it has roller cam followers rather than the flat tappets you have in yours. As it also have a fully rebuilt engine, there's no sludge in there either (although there was when I stripped it down). I suspect the biggest problem with boat engines is that very few have a sump plug, or anywhere to drain the oil into, so most just suck it out the dipstick tube if they actually bother to change the oil at all. My experience is that boat owners tend to treat an inboard engine as that black lump that lives under a cover in the back and gets totally neglected until it stops working.

For the P38, I have used Castrol 10W-60 synthetic on the advice of Ray at V8 Developments after he rebuilt the engine. The P38 workshop manual gives a list of LR recommended oils depending on ambient temperature.

Thanks Gilbert. I very nearly didn't make a public thread on this subject, was going to mention it to you in a PM (for the benefit of others Gilbert and I talk boats in PMs). But the thought occurred that at least the ZDDP aspect would be relevant here too (Rover V8's have flat tappets?) and I knew you'd see and reply to this thread anyway :)

Just spent 3/4 of an hour hand pumping 5 litres of Halfords 20/50 out of the boat engine dipstick tube including a few breaks. Pita job seemed more difficult this time than ever before but that's probably because I have a bad shoulder this time. New oil hasn't even arrived yet.

I tried different oils from 0W-40 to 15W-40 and always had quite a high comsumption of oil. Basically a rolling oil change :-) Be it burning or rather leaking.
Then tried the recommended Valvoline VR1 20W50 and that was a lot better.
I then changed to 15W-50 because the 15W give me a better temperature range for the winter here in Germany, also very little oil consumption, so I will stay with that. Mannol Favorit 15W-50, a lithuanian oil, only around 3 € per litre.

After I had V8 Developments rebuild the engine in my P38 Ray's recommendation was to use Valvoline VR1 20W50 changing oil every 5K miles.

The Valvoline VR1 20/50 arrived today, I put it in but it'll be spring before the boat/engine is used again.

A couple of oils mentioned above including the Valvoline stuff that's high in ZDDP and detergents.

What are thoughts on ZDDP for flat tappet engines, neccessary only during the cam and tappets running in stage or all the time?

How much ZDDP and detergents do the other oils have?

Maybe if people have been using old-skool 20/50 etc oils for a long time it would be a bad idea to switch to the Valvoline stuff because the detergent could dislodge sludge, not problem if they've been running synthetic (which is generally higher in detergents than old-skool mineral)?

Not sure if the Ford or RV8 engines have full flow through the filter or some oil bypasses the filter.

I have been using Delo 400 10w40 in everything I own be it a lawnmower or Cat Diesel in the boat.
Rated the "Best dinosaur based oil available" Seems to do a good job for me.......
As for the issue with oil changes on marine engines?
The solution is very simple and the slight expense involved is well worth it!
Source a thread to barb (or thread to JIC) fitting that will fit the oil pan plug hole, then attach a piece of appropriate
hose to that and then to the suction side of a small brass manual suction pump like one of these:
https://www.newpig.com/action-pump-brass-piston-transfer-pump/p/DRM1415?srsltid=AfmBOoqp0uyAp8qhHkaRItor4pDZLkoxKRQeScghkKCqdocP-5LqfLaf
(There are a bunch out there and the best ones are made in UK!)
A 1/4 turn ball valve can be installed in the suction side if you like as well, but if the pump is mounted with the inlet above the level of the oil in the pan, not really needed.
Oil change is then a matter of sucking the oil out and straight into an empty container.
I have added this to about a dozen boats and a good number of diesel gensets with poor access due to sound proof enclosures.

On my boat engine the dipstick tube connects to the (only) plug / drain hole in the sump. The dipstick tube runs from what would usually be the sump drain hole around the back of and under the sump, the dipstick never actually enters the sump but oil level can be read almost as usual because oil in the dipstick tube finds the same level as oil in the sump - the dipstick only reaches as far as bottom of sump level but on the port side of the engine when the sump hole is on the starboard side.

One of the problems with this is that you can't tell condition of oil in the sump by reading the dipstick because oil in the disptick tube probably never mixes with oil in the sump so always looks cleaner than the oil in the sump after the engine has been run for a few hours. If (say) there was water in oil in the sump, oil on the dipstick still wouldn't look milky because it would be reading oil in the tube pushed into the tube last time we did an oil change. With this setup the dipstick is only good for reading oil level, you can't use it to check oil condition.

The dipstick tube is designed to double up as an oil drain tube using a suitable vacuum pump and even has a threaded connector on top, apparently a 'garden hose type connector' fits to screw such pump fitting onto... but I bought such connector to screw on and it didn't fit.

If I/we did fit a barb and flexible oil removal hose to the sump hole instead of the factory dipstick tube it would mean we wouldn't have a dipstick... But the dipstick tube effectively does the same job as a flexible oil removal hose because it connects to the sump drain hole and doubles as an oil removal tube anyway?

I would still like to have a threaded connector with hose barb to attach to the 'garden hose connector' on top of the dipstick tube and run a pipe from the barb to the oil extraction vacuum pump. I have been using a hand operated oil removal / vacuum pump that has a rubber end that seals to the tube but this means holding the hand pump tightly onto the top of the tube to maintain the seal and it's hard work holding it on and pumping at the same time, especially when the oil is as cold as this weather and with my bad shoulder lol. If I had a garden hose to pipe tail connector I wouldn't need to hold the pump tight on the dipstick tube while pumping so it would make it quite a lot easier.

i haven't owned a boat for 30 years, never had much to do with inboards either, but i can remember they ran a lot cooler than car engines, this may have changed with today's engine set ups, let's face it, nothing is the same as yesterday's stuff. my point being if they are cool runners, you will need a thinner oil than usual. what is the oil pressure and the temperature of the engine when at running temps.

Lpgc wrote:

Thanks Gilbert. I very nearly didn't make a public thread on this subject, was going to mention it to you in a PM (for the benefit of others Gilbert and I talk boats in PMs). But the thought occurred that at least the ZDDP aspect would be relevant here too (Rover V8's have flat tappets?) and I knew you'd see and reply to this thread anyway :)

Do you want a public subforum set up for that? It's no bother...

The dipstick tube on my boat engine is fitted into the sump plug. It's on one side but near enough at the bottom of the sump. It's a solid plug with a threaded hole in the centre where the dipstick tube is fitted. So I can either unscrew the tube from the plug or, once I've done that, unscrew the whole plug. I reckon there is enough room under the engine to get a bowl under it which I can slide forwards out from under the engine if I take the bilge pump out (which sits just under the front of the engine. I've seen pictures of an arrangement where there is a tap instead of the drain plug and a length of hose which can be pushed through the drain hole in the transom which seems a much better idea to me.

Not sure about cooler running. My engine is a 4.3 litre Mercruiser V6 which is nothing more exotic than 3/4 of a 5.7 litre V8 small block Chevy and runs at around 170F. No idea what 170F works out to in proper units but as it is in the middle of the gauge, I assume it is correct. According to the engine manual, the oil pressure at 2,000 rpm should be 30-55 psi and more than 4 psi at idle. I'd be seriously worried if I saw oil pressure below 10 psi even at idle and mine sits at around 50 psi when running, dropping to 35 at idle when hot. So it must like the 15W-40 I've put in it.....

gordonjcp wrote:

Do you want a public subforum set up for that? It's no bother...

Nah but as it's a virtual pub it should probably really be in Opening Time. The place for any random topic not specifically P38 related, just like any real pub.