Need Synthetic Recommendation

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19
Location
TX
New member here and I apologize for the length of my first thread. My '94 Mercedes E420 had run its entire life on Mobil 1 15W-50, without issue. (I am in TX, so the ambient temperature can be quite high, hence the high viscosity.) Then I discovered that Mobil had quietly switched from Group IV and V base stock to Group III base stock, which I viewed as both hypocritical and underhanded. Hypocritical, because Mobil sued Castrol for calling their Group III base stock oils "synthetic" while Mobil did the exact same thing after the ruling was in Castrol's favor; and underhanded, because they did so quietly, without informing their customer base. I switched to Royal Purple HPS 20W-50. My second oil change with Royal Purple was at a 7,200 mile interval, which is significantly longer than my standard 6,000-mile oil change interval. ~ 3 weeks prior to this last oil change, I noticed that my oil pressure gauge was acting wonky (rapid fluctuations, sometimes pegged at max - even at idle, or 1 bar when cruising at 80 mph, when it should have been at 3 bars). Today, I took my vehicle into my Mercedes mechanic for him to check out since I thought it might be an oil pressure sending unit issue. I also had him change the oil and filter (Mann canister filter) with Royal Purple HPS 20W-50. The mechanic said that after the oil change the oil pressure gauge was reading/operating properly, which I confirmed, albeit only briefly. Irrespective of the oil pressure gauge/sending unit, my mechanic stated that there is not an actual oil pressure issue. My concern is two-fold 1) my mechanic said that the oil filter was showing the very first signs of sludge build-up (filminess), which I thought was unusual for a top-tier motor oil such as Royal Purple - even at 7,200 a mile oil change interval, and 2) the oil seems to have interfered with my oil pressure sending unit. Since my vehicle has 240,000+ miles on it, he suggested that I switch to Valvoline 20W50 Extended mileage conventional (Mineral) oil. I found that Valvoline does make a synthetic blend Max Life in 20W50, but they do not seem to have a full synthetic "high mileage" oil in either 15W50 or 20W50. While I understand that synthetic motor oil is not required for my 119 engine, I don't really want to switch back to a conventional motor oil since the vehicle has run synthetic oil for its entire life. Now I'm confused about what motor oil I should use. While I haven't lost faith in Royal Purple just yet, I am concerned about the possible sludge issue - even if it was just beginning to present. The oil pressure interference is another issue that may or may not be attributable to Royal Purple. I would like to use a synthetic oil that is, reasonable priced ~$8.00/qt., relatively easy to source and is a genuine synthetic oil (group IV or V base stock). Liqui Moly and Motul are difficult to find from a US distributor, especially for a decent price, but can be ordered online if I pay a hefty shipping fee. Red Line is fairly expensive. I'm not sure what other 15w50 and 20W50 oils I should consider and I'm not sure if a High Mileage formulation is beneficial or necessary. I am not interested in using Amsoil due to a previous bad experience… or perhaps I should stick with RP? Any recommendations based upon experience would be appreciated. Thank you.
 
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11,195
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USA
welcome Napa carries Liqui-Moly at a fair price. And if your particular store doesn't carry a particular L-M product you're looking for, they can order it with no problem smile M1 0w40 from Walmart is most liokely the cheapest, easiest-to-find oil I'd use on that Benz
 

High_Noon

Thread starter
Messages
19
Location
TX
aquariuscsm: Thanks for the reply. I am currently in El Paso, although I grew up in Dallas. I will be in Dallas soon for a few weeks. The reason I switched from Mobil 1 15W50 is b/c it is not a true synthetic oil - it has a group III base stock.
 

High_Noon

Thread starter
Messages
19
Location
TX
slacktide_bitog: Thanks for the welcome and the recommendation. I will check out the Liqui Moly at my local NAPA. I noticed that both Liqui Moly and Motul both refer to their 15W50 and 20W50 viscosity oils as "Motorcycle" oil - is there anything to that, or any problem using it in a passenger vehicle?
 
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857
Location
Maryland
I'm assuming you're the original owner... If you are not the original owner, do you know the history of the vehicle? What engine is in your 94 E420? How many oil/filter changes have you done on it in the past and what was the interval? Are there any other signs of sludge build-up visible by-way of looking into the oil fill hole? Can you get a bore inspection light to look under the valve cover?
 
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857
Location
Maryland
BTW: There are several models of MB engines that have a characteristic problem with the oil pump pick-up tube. The tube has as rubberized O-ring that eventually hardens and cracks and therefore causes wild fluctuations in oil pressure.
 
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13,194
Location
Maricopa Arizona
Originally Posted by High_Noon
aquariuscsm: Thanks for the reply. I am currently in El Paso, although I grew up in Dallas. I will be in Dallas soon for a few weeks. The reason I switched from Mobil 1 15W50 is b/c it is not a true synthetic oil - it has a group III base stock.
Why too much emphasis on marketing. Focus on the certs and performance this means M-1 is in the top. Also RP has similar cold weather performance in many cases worse performance then group III synthetics thus I doubt it's anything but a high group III content synthetic. At the very least it pumps and flows like a group III based synthetic were PAO is supposed to shine.
 
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23,782
Location
Dallas,Tx USA
Originally Posted by dave1251
Also RP has similar cold weather performance in many cases worse performance then group III synthetics thus I doubt it's anything but a high group III content synthetic. At the very least it pumps and flows like a group III based synthetic were PAO is supposed to shine.
Funny you mention this. I once did a freezer test with a half quart of M1 15W50 vs a half quart of RP 20W50. The RP was literally solidified while the M1 shook around in the jug as if were at room temperature.
 
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2,593
Location
CenTX
8.09$ a quart, free prime shipping. Probably find it cheaper if you have a rep in your area. Pair it with a Mahle or Mann filter and zoomzoom

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Messages
43
Location
New England
Go back to using Mobil 1. Don't get bogged down in base oil types, not only is it irrelevant to your application, but certifications are what matter. But all Mobil 1 blends use some group 4, and it was recently revealed in a previous post (linking to a Russian Oil club) that depicted a gas chromatography test, that they use group 5 in the form of Alkalated Naphthalene, and some blends use POE. Furthermore, a recent trend is that Mobil 1 is using more GTL in place of any group 3 base stocks.
 

High_Noon

Thread starter
Messages
19
Location
TX
RayCJ: Yes, I am the original owner and I have the complete history of the vehicle documented. The engine is the Mercedes 119, 4.2 V8. I have probably done at least 50 (estimated) oil changes in the time I have owned the vehicle - all with Mobil 1 15W50 - and the interval was around 5-6K. There are no other signs of sludge build up by looking into the oil fill hole. I had the valve covers off within the past year and there was no sign of sludge. I will also look into the oil pick-up tube issue you mentioned. Thanks. TheLawnRanger: I used Mobil 1 15W50 for the last 24 years. Only recently did I change to Royal Purple and I have just completed my second oil change with Royal Purple HPS 20W50 - the first at a 6,000 mi interval and the second (just today) at 7,200 miles, which is the longest I have ever run an oil. Dave1251: Thanks, that's good information and I think I recall reading something similar when I was previously researching oils when I changed from Mobil 1 to Royal Purple. aquariuscsm: I heard about Castrol Edge, but I have not looked into it yet. Lotl: Duly noted. It's interesting you mentioned that because when I was researching oils before I switched to Royal Purple I could find no definitive info. regarding the base stock RP used. I even read several cases where people contacted RP to find out but they refused to disclose their formula or what base stock they used. In retrospect, that should have been my first red flag. GumbyJarvis: I've never heard of Schaffer's oil. I will look into it. Ad_infinitum: Good to know Mobil is making changes. I may end up going back to Mobil 1 15W50. ***** As of now, I plan on running this latest batch of RP 5,000 miles and then switching back to M1, Liqui-Moly, or possibly something else... I need more info. on the other choices out there. Thanks for all the advice.
 
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2,416
Location
WY
You are going to be disappointed if you are looking for a mass market motor oil that is prevalent in group IV/V. Most everything has gone to group III with small varying amounts of IV and even smaller amounts of V if any. You may check out Ravenol. Royal Purple I think has gone mostly to III and sometimes adds Synerlec which is an additive that is kind of a mystery to me. https://www.ravenol.de/en/products/usage/d/Product/show/p/ravenol-rfs-sae-15w-50.html

Pipe_Organ_Speakers.jpg
 
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1,318
Location
PEARL River la
As of right now all oils are technically "synthetic ". Conventional oil is now a blend so the oils today you get a name brand you trust for cheapest price that meets spec and sleep well. Oils have come a long way over last decade so with regular oil changes not much of a chance of an oil related problem just a mechanical problem that causes oil to fail (fuel dilution)
 

High_Noon

Thread starter
Messages
19
Location
TX
sloinker: Unless I'm reading it incorrectly the Ravenol website states that the RAVENOL RFS SAE 15W-50 is fully synthetic, while the exact same oil is listed as semi-synthetic everywhere else I look. Yes, it is difficult to find a fully synthetic (group IV or V) motor oil in 15W50. Liqui-Moly, Motul and Red Line seem to be the main choices in a fully synthetic 15W50 motor oil, but they are significantly more expensive than Mobil 1. Both Motul and Liqui-Moly refers to their 15W50 as "motorcycle oil" - not sure if that matters. Mobil 1 seems to be the cheapest and easiest to source, but is not fully synthetic. tiger862: Although I'd rather not do it, I may just have to switch back to Mobil 1 15W50.
 
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