High mileage full synthetic, synthetic blend or conventional in a 263K mile car?

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19
Location
Connecticut
Thread starter
Hi, right now in my 1994 Sentra I'm running Supertech 10w40. I had no real particular reason why I ran it, the car was pretty much on its last legs when I got it and it's been brought back to life somewhat now, to the point it's an around town kind of vehicle. I basically only ran the 10W40 as I had another car a couple of years before with a severe front main seal leak, and I bought it as a 5 quart jug to limp it around before I sold it, and I had 3 quarts left in the jug and the car came with a quart of Formula Shell 10W40, and it's a 3.5 quart car. I put it in, probably in... August or September? It seemed to run smooth then, but I noticed kind of randomly a giant gas mileage drop, from about 23-25 city, to 20-21 city, with cold temperatures finally hitting harder. However, this week it was relatively warm, and I got 25mpg again. So I'm thinking it's a case where the 10w40 doesn't heat up sufficiently in winter, especially with a lot of short trip driving. Also the engine has sludge too, and my oil is pretty much black after these 1500 miles, so I'm hoping to change it out for that reason as well, at least the detergents are working. As it is now, I'm really happy about its oil usage, even with a slight valve cover leak it's only used about 1/4 of a quart in about 1500 miles. This is with non high mileage conventional Supertech 10w40. However, the seals aren't really good at all on it, the spark plug seals were rock solid, along with the valve cover gasket, they just broke into solid pieces by bending them with my fingers when I changed them. So I'm hesitant to try synthetic, though I've had other people tell me they had decent results switching to synthetic on old cars like this (my friend told me he had a sludged up Civic where chunks of sludge came out of the oil pan, and he did 5-6 3K OCIs with synthetic and it cleaned a lot of sludge out...) but I'm pretty scared. At Wal-Mart right now, ST conventional and synthetic are within a dollar of each other. I've also read some conventionals are just secretly synthetic now as well. I think now with more fracking, synthetics are dropping in price due to more natural gas being found? I know even some bulk oil in drums for oil change places are synthetic blends now, as well (place where I briefly worked had 5W30 syn blend bulk oil....) I had a Volkswagen prior to this, and in that with similar mileage (but a lot better shape, except for a cooling system problem and being hard to work on in general...) I alternated between 15w40 Mobil Delvac and 5W40 Rotella. I actually ironically got about 1-2mpg more with 15w40 compared to the relatively fresh 5w30 in it (friend gave me the car, pretty OCD about oil changes and related stuff...) in summer in the Volkswagen, maybe some gains in compression? In winter the 5W40 Rotella seemed to run fine as well, no mileage drop, so that's partially why I felt OK running the 10w40 in the Sentra, figuring the heavy oil thing in cold weather was a myth/overstated. My father personally got 450K out of a Ford Freestar without going into the engine, and driving it to the junkyard with Rotella 15w40 and 3-4K OCIs (in an engine spec'd for 5W20.) With the diesel oils my Volkswagen ran super nice and smooth, so I was thinking of running a 5W40 diesel oil again, but I don't know if it would cause a mileage drop in the Sentra still compared to 5W30 (it says 5W30 preferred under the hood on the sticker, but makes allowances for up to 20w50 in summer...) but most of the 5W40 diesel oils are synthetics or synthetic blends. So, what should I run? Full synthetic 5W30 high mileage, 5w30 conventional, (high mileage or normal?) or a 5W40 diesel oil? Thanks very much!
 
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3,424
Location
Ohio
I'd just run the cheapest quality dino or HM that I could find and call it a day. At 263K, whatever got it there must have had some level of success.
 
Messages
333
Location
NJ
The sudden increase in fuel consumption may have been caused by supplier switch to winter-blend fuel. I've been a fan of high mileage oils which have higher HTHS and/or concentrations of antiwear additives such as moly. No empirical data to show they are more effective than non-HM oils, just observing quieter valvetrains on my vehicles vs. Mobil-1 non-HM in all 3 cases. Pennzoil Platinum HM 5W-30 has been my go-to for quietness on my '07 4Runner. Valvoline MaxLife synth blend 5W-20 is a more recent addition here, using it in my wife's '05 Mercury Mariner and near-zero oil loss on the dipstick at 1.8K miles (too soon to tell if this is an improvement over previous PPHM 5W-20). So...I'd go with HM oil. Pennzoil High Mileage has been a good conventional option for me and a neighbor I help, it's cheap. PPHM if you want to pop for synthetic, however for your specific vehicle I'm not certain you'd see any incremental value versus the conventional version.
 
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15,358
Location
In the shop
Originally Posted by Triple_Se7en
Just stay with what's working for the aged vehicle. Don't even change brands. Use 10w30 conventional in winter and 10w40 in the spring, summer and fall.
Yep, use 10w30 year round smile
 
Messages
887
Location
Pennsylvania
Just my opinion, for what it is worth, but 5w-30 oils seem more appropriate for your climate. I ran Mobil1 0w-40 in the Volvo in my signature for a couple of years while towing with it. Its been back in the xw-30 camp for the last two years with no ill effect.
 
Messages
8,264
Location
Virginia
Originally Posted by 53' Stude
Originally Posted by Triple_Se7en
Just stay with what's working for the aged vehicle. Don't even change brands. Use 10w30 conventional in winter and 10w40 in the spring, summer and fall.
Yep, use 10w30 year round smile
I agree with the guys here ^^^^^^ I had a 95 Nissan Sentra... A very good car for 5 years I had it. I got the car with 118k miles on it Timing chain broke at 242k miles in the Wendy's drive thru... Of all places LOL
 
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Messages
4,085
Location
Los Gatos, CA
Since it's cheap, I would run ST Synthetic HM 5w30 or 10w30. I might even run some of that Motor Mouth stuff at next oil service to de-sludge it. Heck, go for 300K.
 
Messages
921
Location
D/FW Metroplex
I had a slight oil drip on my 100K mile Hemi, ran several OCIs of Valvoline Maxlife HM and the drip stopped. Then ran a couple OCIs of SuperTech Synthetic HM, and the drip came back but was more of a drip-drip now. Switched back to Valvoline Maxlife HM and the engine has once again stopped dripping after 3 OCIs. Is the oil responsible for the oil leak-not-leak-not behavior? I don't know, but it is a strange couple of coincidences if not. Take from that what you will, but if it were my car, I'd leave the full synthetic (even HM synthetic) alone and switch to some good HM conventional or HM semi-syn and run that until the car take The Big Dirt Nap on you.
 
Messages
8,264
Location
Virginia
Originally Posted by 53' Stude
Originally Posted by 4WD
The sprockets freaked out over square meat …
Take it easy on Bradley. He does what he can grin2
Ohh don't worry 53. . I give 4wd a hard time quite a bit on here... He needs it... Try to maintain his sense of levity LOL
 
Messages
19
Location
Connecticut
Thread starter
Originally Posted by The_Nuke
I had a slight oil drip on my 100K mile Hemi, ran several OCIs of Valvoline Maxlife HM and the drip stopped. Then ran a couple OCIs of SuperTech Synthetic HM, and the drip came back but was more of a drip-drip now. Switched back to Valvoline Maxlife HM and the engine has once again stopped dripping after 3 OCIs. Is the oil responsible for the oil leak-not-leak-not behavior? I don't know, but it is a strange couple of coincidences if not. Take from that what you will, but if it were my car, I'd leave the full synthetic (even HM synthetic) alone and switch to some good HM conventional or HM semi-syn and run that until the car take The Big Dirt Nap on you.
So you'd say the Valvoline Max Life is good stuff for leaks? It's only $3-4 or so more than Supertech at Wal-Mart, so it might be worth a try. What about the NAPA oils that are synthetic blend? I just realized from reading on here they're made by Valvoline, but I missed their last sale, it was only $13 per gallon or 5er then.
 
Messages
1,792
Location
South Carolina
Originally Posted by JeffKeryk
Since it's cheap, I would run ST Synthetic HM 5w30 or 10w30.
Agree. Sounds like this engine hasn't had a good oil changing life. This would be my recommendation.
 
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