Heavier oil?

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1991 Chevrolet K1500, 4.3 V6, 116k miles (estimated, due to broken odometer). Has had bad valve stem seals since I purchased it five years ago with 89k miles. Always a blue puff of smoke on startup. I can't tell if it is smoking badly now. Lately, it is starting to use a lot of oil. A quart every few months. I don't know if this could be from the bad stem seals, or if rings are getting worn? I might mention that this vehicle is a short tripper. I was doing once-per-year oil changes. Thinking I am doing about 6k miles per year or less. Decided I will start doing twice-per-year oil changes due to the short trips. Wondering if a 40 weight oil will reduce consumption. I've been using a 5w/30 as spec'd (although I put 5w/20 this last oil changed because that's what I had on hand). Thinking of going to a 5w/40 or 10W/40, for summer. Maybe even a 15W/40. Thoughts and suggestions welcome.
 

Astro14

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Couldn't hurt... Look, if you're driving 6,000 miles/year, and you're adding a quart every "couple" of months, then you're adding a quart every thousand miles or so, which isn't terrible. In fact, with blue smoke on startup, it's probably just the valve stem seals...nothing else...and heavier oil may help with that. Valve stem seals aren't a hard job on this. But heavier oil is cheap. Might as well see how it works.
 
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Nope on the 40. Garbage oil. Run the 5W30, your hydraulic lifters need a certain leakdown rate. to give you good torque and fuel economy. You should NOT have run the 20 grade oil! Just do the Stem seals if the compression test points that way, easy enough job. but is suspect it was just a neglected and carboned up rings and pistons. Thicker oil is usually never the solution unless t you have big miles, and you dont.
 
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SR5

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Originally Posted by Astro14
Couldn't hurt... ..... Valve stem seals aren't a hard job on this. But heavier oil is cheap. Might as well see how it works.
Exactly, just give it a go, it's not going to hurt anything. I've swapped between 5W30 synthetic and 15W40 mineral a few times. It all works.
 
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Sounds like valve stem seals also to me. If your not gonna replace those -- move to a 10W30 or 10W40 High Mileage motor oil during summer months.
 

CT8

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Originally Posted by otis24
I put 5w/20 this last oil changed because that's what I had on hand). Thoughts and suggestions welcome.
interesting
 
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Sometimes we are better off donating 5w20 oil to the Vietnam Vets Club, than use it because it's sitting in the garage. I once put 5w20 in my 4.3 S10 and when I changed the oil 5K later, the magnetic drain plug was loaded with shiny silver shavings. The idea to move up to 10w40 in South Dakota is your best idea, if you are not mechanically-inclined to fix the oil loss yourself.
 
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Originally Posted by otis24
1991 Chevrolet K1500, 4.3 V6, 116k miles (estimated, due to broken odometer). Has had bad valve stem seals since I purchased it five years ago with 89k miles. Always a blue puff of smoke on startup. I can't tell if it is smoking badly now. Lately, it is starting to use a lot of oil. A quart every few months. I don't know if this could be from the bad stem seals, or if rings are getting worn? I might mention that this vehicle is a short tripper. I was doing once-per-year oil changes. Thinking I am doing about 6k miles per year or less. Decided I will start doing twice-per-year oil changes due to the short trips. Wondering if a 40 weight oil will reduce consumption. I've been using a 5w/30 as spec'd (although I put 5w/20 this last oil changed because that's what I had on hand). Thinking of going to a 5w/40 or 10W/40, for summer. Maybe even a 15W/40. Thoughts and suggestions welcome.
How about Maxlife 10w30 blend
 
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Originally Posted by 53' Stude
Originally Posted by otis24
1991 Chevrolet K1500, 4.3 V6, 116k miles (estimated, due to broken odometer). Has had bad valve stem seals since I purchased it five years ago with 89k miles. Always a blue puff of smoke on startup. I can't tell if it is smoking badly now. Lately, it is starting to use a lot of oil. A quart every few months. I don't know if this could be from the bad stem seals, or if rings are getting worn? I might mention that this vehicle is a short tripper. I was doing once-per-year oil changes. Thinking I am doing about 6k miles per year or less. Decided I will start doing twice-per-year oil changes due to the short trips. Wondering if a 40 weight oil will reduce consumption. I've been using a 5w/30 as spec'd (although I put 5w/20 this last oil changed because that's what I had on hand). Thinking of going to a 5w/40 or 10W/40, for summer. Maybe even a 15W/40. Thoughts and suggestions welcome.
How about Maxlife 10w30 blend
Sounds like a good plan. Try a 10W30 hm oil.
 
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when the spec 5-20 went thu girlfriends 2.5L 13 oil burning malibu i switched to 10-30 which helped a while, then to a 5-40 + as it was using over a qt on a thou at only 60 thou she dumped it for a preowned optima 2.4 L that uses NONE. sooner or later yo might need to trade or fix or just keep dumping in the oil!! i was using 20-50 in my 72 nova, ok until it got cold + would not crank fast enough to start!!
 
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Worn valve stem seals are common on 4.3's, but very easy to replace with proper tools. Small tidbit on a truck my dad once owned: https://www.bobistheoilguy.com/forums/ubbthreads.php/ubb/showflat/Number/5096175/Searchpage/1/Main/308717/Words/4%5C.3+/Search/true/re-my-auction-find-1996-chevrolet-c1500-w-t#Post5096175
 
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Originally Posted by skyactiv
Worn valve stem seals are common on 4.3's, but very easy to replace with proper tools. Small tidbit on a truck my dad once owned: https://www.bobistheoilguy.com/forums/ubbthreads.php/ubb/showflat/Number/5096175/Searchpage/1/Main/308717/Words/4%5C.3+/Search/true/re-my-auction-find-1996-chevrolet-c1500-w-t#Post5096175
That's not that bad on that engine at all. The one and only time I've done valve seals was on a transverse 6. It was a PITA doing the bank 1 valves due to things being so "tight" and having to reach back in there and the plenum and throttle body had to come off so that added time. By comparison bank 2 was a breeze, the valves were staring right at you with tons of room to work..any way you cut it, it's still a bit of work for some stupid small seals but totally doable if you're patient/attentive to detail and halfway mechanically inclined.
 
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Originally Posted by Olas
a leakdown test will tell you where the oil is leaking into the cylinder. replace the worn/faulty component.
No. Leak down can't test the integrity of valve seals. Valve Seats, rings, and head gasket yes.
 
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Had a fleet of C1500 Chevys with 4.3 engines. Use the GM style o ring valve seal along with the umbrella seal over the valve guide boss. Double protection especially if there are worn guides. The umbrellas alone won't stop the oil usage on any SBC V8 or V6.
 

otis24

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I plan on running this truck another ten years, unless I hit the lottery. The body is more likely to fall apart before the engine goes, even with some oil consumption. This truck has been a short-tripper for the last twenty years. The school I work for purchased it with 56k miles on it when it was five years old. They put less than 2000 miles per year on the vehicle, driving it around campus. The oil was changed once per year with about 1200 miles average on the oil. Mobil bulk conventional oil. I am guessing that the short tripping wasn't good for this vehicle. I just need to keep a closer check on the oil. If I can't find a good deal on a 5w/40, I may try adding a straight 30 wt for a while then move to a 10W/30 or 10W/40 next oil change. Current fill is Havoline 5W/20 HM. Will have to try to thicken that up a bit as it with a heavy top off oil as it consumes.
 
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Sit down with the Campus Board of Trustees and tell them longetivity for this vehicle depends on someone taking the truck off-campus and on the freeway every two weeks for at least 15-20 minutes of higher speeds driving. Tell them you will do it and not leave any McDonald's wrappers on the backseat floor.....lol
 
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Originally Posted by otis24
I plan on running this truck another ten years, unless I hit the lottery. The body is more likely to fall apart before the engine goes, even with some oil consumption. This truck has been a short-tripper for the last twenty years. The school I work for purchased it with 56k miles on it when it was five years old. They put less than 2000 miles per year on the vehicle, driving it around campus. The oil was changed once per year with about 1200 miles average on the oil. Mobil bulk conventional oil. I am guessing that the short tripping wasn't good for this vehicle. I just need to keep a closer check on the oil. If I can't find a good deal on a 5w/40, I may try adding a straight 30 wt for a while then move to a 10W/30 or 10W/40 next oil change. Current fill is Havoline 5W/20 HM. Will have to try to thicken that up a bit as it with a heavy top off oil as it consumes.
Originally Posted by otis24
I plan on running this truck another ten years, unless I hit the lottery. The body is more likely to fall apart before the engine goes, even with some oil consumption. This truck has been a short-tripper for the last twenty years. The school I work for purchased it with 56k miles on it when it was five years old. They put less than 2000 miles per year on the vehicle, driving it around campus. The oil was changed once per year with about 1200 miles average on the oil. Mobil bulk conventional oil. I am guessing that the short tripping wasn't good for this vehicle. I just need to keep a closer check on the oil. If I can't find a good deal on a 5w/40, I may try adding a straight 30 wt for a while then move to a 10W/30 or 10W/40 next oil change. Current fill is Havoline 5W/20 HM. Will have to try to thicken that up a bit as it with a heavy top off oil as it consumes.
5w20 is a little light for that era of 4.3. Anything with 30 or 40 weight is appropriate. After driving, remove the oil fill cap and look in the valve cover to see if oil is ponding on top of the head. If so the oil drain back holes are sludged and causes the oil to reach a level that can be drawn down the valve guides. It's then as simple as removing the valve covers and cleaning the sludge out of the drain backs. Both ends of the heads.
 
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