Should I go to a full syhthetic or use a synthetic blend

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2
Location
USA
Hello everyone, I have some questions about oil I would like to ask. I have a 1991 Chevy K1500 Silverado pickup with a 4.3 V6 engine. The truck now has about 180,000 miles on it, and I am the only person to change the oil since I purchased the vehicle new. I have only used Castrol GTX 5W-30 conventional oil and NAPA / Wix filters and I have changed the oil & filter about every 3,000 miles. When the vehicle was new, I actually did the first change at about 500 miles, another at about 1,500 and then started a 3,000 change interval after that. The oil specified for this engine when it was new was actually SG. Originally, I went with a plain conventional oil because back in 1991 there seemed to be a big difference in the price of synthetic oil and conventional oil. Also, at that time, I had concerns that synthetic might cause the front or rear main bearing seals to leak, but as I understand it, that is no longer a problem with modern synthetics. Recently I was only able to purchase Castrol 5W-30 in the Ultraclean synthetic blend, however the price went up to about $ 29.00 for a 5 quart container. I contacted Castrol but they would not tell me what percentage of the Ultraclean is synthetic and what percentage is conventional oil. I want to stick with Castrol oil. Since there is not that great of a price difference between the synthetic blend and the full synthetic castrol in a 5W-30, should I go with either the "Edge" or Magnatech full synthetic, or just stick with the Ultraclean ? I mainly want to make the engine last as long as I can. I'm not really interested in the "high mileage" Castrol, because as I understand it, the high mileage oil has seal conditioners that may swell seals. I do not currently have a seal leakage problem, so I do not want to swell the seals and cause them to wear, I would rather keep the seals as they are. Also, the high mileage is still a synthetic blend and not full synthetic. Castrol offers the highest engine warranty for Edge, then Magnatech, and then Ultraclean. I can't use a warranty, but I'm thinking this may give a little clue as to which oil might make the engine last the longest. I think there was a Volvo that got over 2 million miles on plain GTX conventional and is till going, but this was probably all highway miles. I mainly drive about 16 miles to and from work everyday, mostly highway, but I do make a lot of short trips two days out of the week. Last winter in Ohio, I think it got down to about 10 below and with the regular conventional Castrol 5W-30, the engine cranked over so slow I did not think it was going to start and it did take a little longer to get oil pressure. This is one reason I am thinking a full synthetic may be the way to go now that there is less of a price difference with the synthetic blend. The engine still seems to run like it did when it was new, same oil pressure, no bearing noise on startup or lifter tick or anything, no smoking. The last oil change I went to about 4,000 miles and it seemed to use about 1/2 quart of oil in that time. If anything goes out, I tend to think it might be a timing chain, but I think by 1991 they did away with the nylon camshaft gears and went to a metal gear didn't they ? If the timing chain has a metal cam gear and a tensioner I would feel better about getting more miles out of it, but I have not looked at it and don't know the exact arrangement. I am pretty sure this engine has rollers on the hydraulic valve lifters that mate with the cam lobes. I am leaning towards going with the lowest priced Edge Castrol synthetic at my next oil change and then sticking with that. Please let me know what you guys would recommend. I would appreciate any feedback. Thanks for your help. Sincerely, John
 
Messages
3,666
Location
St. Charles County, Missouri
Most SN+ conventional oils are roughly 50 percent group 3. (unless there's Mobil base stocks which can meet the spec with Group 2+). So you're running a blend that says it's conventional. With that engine any modern oil is way better than what it came with. I'd think a 5k OCI with any of those oils would be perfectly fine, or any other oil that meets SN+ that you can get cheap. Given the low price spread I'd go with the cheapest group 3 I could find. Didn't ST just drop prices? Their HM synthetic is really cheap i think.
 
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Messages
4,161
Location
Texas
I can not think of any reason to drastically change what you are doing . However , I see no problem with going full synthetic . Especially in cold weather . If you figure the price / cost difference per mile , should be pretty small . We own a 1991 Caprice 5.0l . Best of luck to you , :-)
 
Messages
7,054
Location
Wet side WA
Yes Supertech is currently on Rollback for under $15 a Jug. But then for two dollars more you can pick up the Havoline econobox Pro DS in 6 quarts.
 
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Messages
446
Location
Rochester, NY
That 4.3 v6 is a nice bulletproof engine. I had one in a 1997 Sonoma. It got nothing but Mobil 1 for the first 100k (My friend bought it new, then sold to me at 92k) and mostly Super Tech Syn for the next 100k. It never lost a drop of oil between changes, ever. I think that the oil you are using in that engine is the least of your concerns. Keep the sump full, change it regularly, and pay attention to the other maintenance that is more likely to kill the truck. But, if you are in the cold part of OH and it hasn't rusted apart already in the last 28 years, you are definitely doing the right things!
 
Messages
1,863
Location
NoVA
That few miles between changes a synthetic will not really help in that motor. I'd personally run a 5w30 high mileage oil. HM oils are generally semi-syn and have extra additives that may help in a older/higher mileage motor like yours.
 
Messages
4,030
Location
WA
Dude, if you can take that Ultraclean back. It's only $15 for 5qts at Wally's.com!!! That aside, I wouldn't change a thing. Sounds like what you've been doing is working just fine. But if you must change, that Ultraclean gets good reviews on other forums I'm on. Maybe there's UOA's of it on BITOG??..Castrol claims it's one of the best cleaning oils on the market and at your oci a syn blend should do just fine. [Linked Image]
 
Messages
4,030
Location
WA
Originally Posted by Jimzz
That few miles between changes a synthetic will not really help in that motor. I'd personally run a 5w30 high mileage oil. HM oils are generally semi-syn and have extra additives that may help in a older/higher mileage motor like yours.
At 180k a switch to a HiMi might keep those seals from leaking anytime soon (an oz of prevention right?)..good idea.
 
Messages
3,401
Location
Outer Banks, NC
With your truck's age and solid maintenance history, I'd keep doing what you're doing. Castrol GTX 5w-30 in the white jug is a solid synthetic blend, and it's also on sale on Amazon. Another good option would be the GTX High Mileage in the green bottle.
 
Messages
7,054
Location
Wet side WA
Originally Posted by Mad_Hatter
Originally Posted by Jimzz
That few miles between changes a synthetic will not really help in that motor. I'd personally run a 5w30 high mileage oil. HM oils are generally semi-syn and have extra additives that may help in a older/higher mileage motor like yours.
At 180k a switch to a HiMi might keep those seals from leaking anytime soon (an oz of prevention right?)..good idea.
I just buy what's on sale and oh contraire to popular BITOG myth it has never caused a problem with my Corolla in 135+K still no leaks. The last HM I bought was PUP from Walmart for $14 a Jug and believe it or not they actually finally came through with a rebate 1 for 3. By the way I have probably used it off and on now four of five times. But not in the last 30K however I will likely use up some of that cheap oil again in the next year or so.
 
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CT8

Messages
15,392
Location
Idaho
I will ask what are you anticipating from the change? Cold drops the cranking volts and amps the starter gets. Switch to a syn and see if you benefit, it will not break the bank.
 
Messages
2,584
Location
wv
The Castrol that you are buying now is alot better than it was 28 years ago when you started. I wouldnt think twice about just keeping up what you are doing. For your sub zero temps.. i would just buy a dipstick heater from tractor supply or amazon and keep on truckin'. However if u said you wanted to go to 10K drains...i would advise on a full syn. If it were mine i would buy it from Wally at the price above..and use a Supertech Oil filter.. with 3K drains.
 
Messages
6,638
Location
South Florida
Dude its a 30 year old truck with high miles and been on conventional oil its entire life. You want leaks galore? DO NOT put synthetic oil in that thing. You didn't say where you live, but Id use 10W30 for the south and 5W30 if you live up north. Year round. The cheapest dino you can find. Your timing chain/gears are probably shot at that age and mileage, from what I have seen.
 

wtd

Messages
2,749
Location
southwest Mo.
I say you would be fine sticking to what you have been doing. I don't run full synthetic in any of my vehicles including my newer 14 Mustang GT. Everything gets a blend. I have a 98 chevy K1500 with the 5.7L that I bought new and except for a few years in the early 2000's,(Mobil 1 synthetic) I've always run a conventional or synthetic blend in it and at 138,000 miles, it still runs very strong with the same oil usage it's had since new.
 
Messages
9,503
Location
Virginia
Originally Posted by bubbatime
Dude its a 30 year old truck with high miles and been on conventional oil its entire life. You want leaks galore? DO NOT put synthetic oil in that thing. You didn't say where you live, but Id use 10W30 for the south and 5W30 if you live up north. Year round. The cheapest dino you can find. Your timing chain/gears are probably shot at that age and mileage, from what I have seen.
^^^^^^^^^ I agree... Keep it simple.
 
Messages
4,030
Location
WA
I believe all oil contains some type/amount of seal conditioning agent (plasticizer). HiMi formulas just have more (and maybe different types). HiMi formulas also usually have better detergency which helps dissolve deposits that may be preventing the seal from being properly conditioned (exposed to the lube).
 
Messages
738
Location
New Hampshire
Originally Posted by kstanf150
Shell RTG Truck $11.60 a jug after rebate Why not It's the best deal in town till December 31st
Winner winner chicken dinner! Best deal this year! If I was smart I'd buy enough to last me ten years - I know you can only do 4 per house hold - but there's a lot of houses on my street.
 

john2019

Thread starter
Messages
2
Location
USA
Thanks for all the feedback guys, I appreciate it. I used to buy the 5 quart Castrol jugs at K-mart or Meijer for about $16.00. Meijer stopped selling it where I am at, and they just closed the last K-mart store that was close to me. I got the last jug at Autozone, but I did not shop around, I thought the price just went up becasue it was now a synthetic blend. I don't remember seeing synthetic blend on the stuff I bought from Meijer or K-mart. I can check out Walmart too it's just a longer drive for me. Perhaps I will just stay with the Ultraclean GTX.
 
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