The early PRV engines were noted with failures (Camshafts wear) on the ones mounted on the '70 Volvos, including some of their early '80s 700 series, especially the B27 & B28 engines. But for some reason, Renault & Peugeot cars with the same PRV didn't suffer the same issue, at least, that i heard off. Some claimed it was caused by engine oil recommended, while the rest blamed the Swedish engineers for not getting the cylinder heads in theirs right, unlike the Peugeot & Renault engineers. By the time the Swedish engineers got it right in their improved PRV engine in the late '80s, the B280, the PRV reputation in Volvo was already tarnished that they had to pull out from the venture, leaving Peugeot & Renault to continue in the joint V6 engine production, hence, the PR V6 Engines.

The PR ES V6 engines had a major shift from the predecessors (PRV) in the early '90s since the PRVs were 90° V6, while the PR ES engines were 60° V6, among other designs change. However, some users still consider bottom part of the engine of both as the same, at least, similar. Hence, they believe the ES engines were meant to run only with the same oil with the PRV. Their opposition is not with the 10w-40 that both PRV & PR engines were recommended to use, but with the 5w-40, especially the last PR engine produced and mounted in Peugeots in the late '00, the ES9A V6 engine.

Some PR ES9J4 V6 Engine users do project onto the ES9A, that since the bottom of ES9A & ES9J4 are the same, then only 10w-40 oil must be used on ES9A, and they are terrible wrong. As an owner of 2 ES9A V6 engines, I can authoritatively emphasise again how wrong they are. 5w-40 remained the best oil Peugeot recommended for that engine, not because of what Peugeot said, but because of observable reality called facts, even with the shortcomings of running the 5w-40 on ES9A (will come to that later). As most, if not all ES9A users must have experienced, the engine makes an uncomfortable annoying loud friction sound at cold start, almost every single time, and goes away till engine becomes dead cold again (like about 10 hours or more after switching off engine). Some claimed the VTC sprockets are the culprit. Some concluded the camshaft rockers are. Whichever the cause is, it's one of the downsides of owning ES9A. I would be surprised if yours hasn't started. However, when you run 10w-40 in it, the noise tends to be frequent even when engine is very hot (like 10 minutes or less after switching off a hot ES9A), and even sounds louder and last longer than the 5w-40 does. The ES9A engine note isn't aggressive as the early PRVs it replaced, but it has the V6 signature as the rpm climbs towards the red zone. But at idle when the engine is hot, you would only know the engine is running when you look at the tachometer or peep at the Auxiliary belt chamber under the hood. That's how quiet the ES9A usually is with 5w-40, which unfortunately you will lose when on 10w-40. It doesn't mean 10w-40 is bad for the engine. It simply means it's not the best for it.

The ES9J4S V6 engine (the direct predecessor of the ES9A) doesn't care much if it's running on 5w-40 or 10w-40, even though its successor does. Just because they all share the same bottom (all the ES engines) doesn't mean the cylinder heads are the same. The 5w-40 is best for ES9A, even in temperate or hot countries. We experience 35° - 45° Celsius sometimes here in Abuja, yet none of my 2 ES9A would pop oil pressure issue, while the temperature remained below 140°C, even with aggressive hard acceleration on these engines in some of these extremely hot afternoons, while I am on fundrive, year after year, same Engine, no oil burn or smoke. So, when next you try to come up with how bad 5w-40 is for the ES9A, understand how nonsensical your position would sound to me.

Of course, I would admit one major downside of running 5w-40 in an ES9A. The engine would hardly be dry. Always expect it to be wet, not necessarily dropping oil, as long as the notorious Cylinder head cover seals/gaskets are not leaking at the time, including the other engine seals (Camshafts & Crankshaft). But I still never had to top up before oil change is due, even though the engines would be wet. Most times, the source or cause are the 2 VVT solenoids that can't help but spit oil (major weak components on ES9A, compared to the indestructible ES9J4S VVT solenoid).

One thing I know most vehicle users lack is the understanding of certification marks when it comes to engine oils for their engines. Also as an IP professional, I very well understand why these marks are very important in selecting or choosing which oil is best for your engine. Just because an oil container has 10w-40 or 5w-40 sticker on it doesn't mean it's good for your ES V6 Peugeot engine. In other words, not all 10w-40 and 5w-40 are good for your engine. Look out for the ones Peugeot has already tested for you and certified good enough for your engine, indicating Peugeot oil certification codes for your engine. Not having your engine oil code doesn't mean it's a bad oil, but just not for your engine. If you are after 5w-40 for the PR ES9A & ES9J4S, look out for PSA B71 2296 on the oil container or research further on the oil for the mark. Likewise, if you are after 10w-40 for your ES engines, insist on PSA B71 2300 mark on the oil. These marks could change, but they are always updated by Peugeot on their service manuals, etc. I honestly don't give a rip about oil international standards like the ACEA and the likes. I care more or focus more on what an engine manufacturer says or recommends for its engine, after some practical tests of the oil has been carried out in their well equipped laboratories or/and out on the road, to determine if the oil meets the engine requirements. But some people, either ignorantly or intentionally, choose to do these tests or experiments on their engines themselves to either prove Peugeot right or wrong, which is OK, as along as you don't bitch about the consequences, incase you get results you don't like.

Total Quartz 9000 5w-40 and Mobil Super 3000 5w40 have both proven on my 3 Peugeot-Renault ES V6 Engines that Peugeot was right all along.

Lion-King Monk.