I drive a 1991 GMC Jimmy S15 with a 4.3L v6 (127,000 miles). I'm getting ready to change the oil again before a road trip, and am not really certain of what to use. Last change (2,700 miles ago) I had Jiffy Lube fill it with their recommended no-name 5w30. Ever since, it has seemed to run a bit more "rough" on hot days (especially on acceleration). Could anyone please give me a weight suggestion with reasoning, and explain to me whether or not I should change to synthetic at this mileage (I'm not the original owner and the mentioned oil change is the only one I've done on it). I've read that it may not be wise with seals and whatnot, but I'm somewhat clueless to this aspect of maintenance. I'm also not sure if high-mileage oils are worth messing with, or if so which ones won't ruin any seals. Thanks for any help fellas (I should add, I live in central Virginia where the temperature range is usually between 100F-5F)
New guy, oil weight question
- Thread starter Hunter0811
- Start date
- Status
Well, you're in luck. 5w30 is the recommended weight for your truck. However, GMC lists several alternative oils based of the climate you live in. As long as it is always above 0F, then you can use 10w30 or 15w40 if it gets really hot. I recommend the 10w30, but you could always experiment with the 15w40 since GMC lists it as being an alternative oil for your engine.
As for the synthetic oil, go ahead and use it. Many people used to believe that if you start to use it on a high mileage engine, the "sludge" will get dislodged and your seals will leak. This is only true if your engine is all sludged up. Take off your oil cap and look down in. If it looks pretty clean other than some minor varnish stains, then you have no worries switching to a synthetic. Actually, even conventional oil has so much detergents in them these days, as long as the oil was changed by the previous owner regularly, then the engine should be very clean.
And finally for the High Mileage oil, my opinion is that if the motor doesn't leak oil then why bother with High Mileage oil. Others will instsntly chime in and bash me for saying such things... just wait and see. If the engine seals are not leaking, are in good shape, then why on Earth would you want to use a High Mileage oil that will cause them to swell up? If it ain't broke, don't fix it. Most non-High Mileage oils contain additives that will condition the seals anyways without the unneccesary swelling that some High Mileage oils deliver.
Long story short, my opinion would be to just buy a good 10w30 oil and go with it. Conventional oil is fine, but I prefer to use Mobil 1.
As for the synthetic oil, go ahead and use it. Many people used to believe that if you start to use it on a high mileage engine, the "sludge" will get dislodged and your seals will leak. This is only true if your engine is all sludged up. Take off your oil cap and look down in. If it looks pretty clean other than some minor varnish stains, then you have no worries switching to a synthetic. Actually, even conventional oil has so much detergents in them these days, as long as the oil was changed by the previous owner regularly, then the engine should be very clean.
And finally for the High Mileage oil, my opinion is that if the motor doesn't leak oil then why bother with High Mileage oil. Others will instsntly chime in and bash me for saying such things... just wait and see. If the engine seals are not leaking, are in good shape, then why on Earth would you want to use a High Mileage oil that will cause them to swell up? If it ain't broke, don't fix it. Most non-High Mileage oils contain additives that will condition the seals anyways without the unneccesary swelling that some High Mileage oils deliver.
Long story short, my opinion would be to just buy a good 10w30 oil and go with it. Conventional oil is fine, but I prefer to use Mobil 1.
Originally Posted By: Hunter0811
I drive a 1991 GMC Jimmy S15 with a 4.3L v6 (127,000 miles). I'm getting ready to change the oil again before a road trip, and am not really certain of what to use. Last change (2,700 miles ago) I had Jiffy Lube fill it with their recommended no-name 5w30. Ever since, it has seemed to run a bit more "rough" on hot days (especially on acceleration).
Unless that oil was somehow defective, it wouldn't contribute to the engine's roughness. 5w30 should work fine. You could step up to a 15w40 if it consumes oil or is very worn, or if you just want to try something thicker. You'll get a little better protection and a little lower fuel economy.
I drive a 1991 GMC Jimmy S15 with a 4.3L v6 (127,000 miles). I'm getting ready to change the oil again before a road trip, and am not really certain of what to use. Last change (2,700 miles ago) I had Jiffy Lube fill it with their recommended no-name 5w30. Ever since, it has seemed to run a bit more "rough" on hot days (especially on acceleration).
Unless that oil was somehow defective, it wouldn't contribute to the engine's roughness. 5w30 should work fine. You could step up to a 15w40 if it consumes oil or is very worn, or if you just want to try something thicker. You'll get a little better protection and a little lower fuel economy.
I also live in Central Va and use 0W30 to 10W30 depending on the vehicle. Newer ones I use the 0W30 and have for years, does fine but will only find in a synthetic. IMO I would use the 5W30 (assuming that is what the manual says) year round and not go to a synthetic. At your mileage no use taking a chance with synthetic, I have swithched at lower mileage and had some seepage issues. The conventional oil is fine. If no consumption or leaking stay with the non high mileage oils, no need.
If engine rough, well, doubt it has anything to do with oil, look for other symptoms.
If engine rough, well, doubt it has anything to do with oil, look for other symptoms.
I'd go with either Havoline DS 10w30 or Quaker State 5w30; Havoline is on the thinner side of the 10w30's and QS is on the thicker side of the 5w30's. If your truck doesn't burn any oil, you can stay with 5w30's with no problems. I don't see the advantage to going synthetic unless you are planning to tow a trailer on your trip.
Hop on the interstate, set the cruise, and enjoy the ride.
Hop on the interstate, set the cruise, and enjoy the ride.
A GM v6 4.3 does not need a thick oil or 15w40
,,any good 5w30 will protect fine in the desert heat,if you want a little edge against that heat throw in some $20 Pennzoil Platinum 5w30 or Mobil 1 5w30 or Mobil 1 Advanced Fuel Economy 0w30,you can get it at wal-mart for cheap plus Mobil 1 has a rebate out for $10 off so Mobil 1 for $12 sounds like a winner to me??
stick with the 5-30,that 4.3 needs all the help it can get with mileage,i've had two of them engines also,great run forever.
stick with the 5-30,that 4.3 needs all the help it can get with mileage,i've had two of them engines also,great run forever.
I have a 4.3 in my S10 ZR2, and had some leakage issues when I switched to synthetic, specifically from the remote oil filter lines. Added some Bars-Leaks, and it has stopped. I'm going back to conventional when I change the oil this weekend. 5w30 in winter, 10w30 in summer. I actually used MaxLife Full Synthetic 5w30, and leaks started. I've read that High Mileage oils with the remote lines on some of the 4.3 engines can actually cause leaks to appear near the filter-end of the lines. If you're isn't leaking now, it's not broke, so don't fix it! Stick to the conventional, in my opinion. 10w30 should do you well for this time of year!
Edit, my engine had 89k on it when I switched from conventional Valvoline to the synthetic.
Edit, my engine had 89k on it when I switched from conventional Valvoline to the synthetic.
Last edited:
Them remote oil lines will leak with any oil,i've replaced many(PITA)and they still leak new with time,bad design of the line.
Originally Posted By: daman
Them remote oil lines will leak with any oil,i've replaced many(PITA)and they still leak new with time,bad design of the line.
I definitely agree that it was a bad design. Mine is a 4x4, but even with the front differential and transfer case, there is still enough room around the motor that they shouldn't have had a need for a remote filter. They accomplished nothing other than adding a "weak link" to the system.
Them remote oil lines will leak with any oil,i've replaced many(PITA)and they still leak new with time,bad design of the line.
I definitely agree that it was a bad design. Mine is a 4x4, but even with the front differential and transfer case, there is still enough room around the motor that they shouldn't have had a need for a remote filter. They accomplished nothing other than adding a "weak link" to the system.
Originally Posted By: Alex38
Originally Posted By: daman
Them remote oil lines will leak with any oil,i've replaced many(PITA)and they still leak new with time,bad design of the line.
I definitely agree that it was a bad design. Mine is a 4x4, but even with the front differential and transfer case, there is still enough room around the motor that they shouldn't have had a need for a remote filter. They accomplished nothing other than adding a "weak link" to the system.
yes sir..
Originally Posted By: daman
Them remote oil lines will leak with any oil,i've replaced many(PITA)and they still leak new with time,bad design of the line.
I definitely agree that it was a bad design. Mine is a 4x4, but even with the front differential and transfer case, there is still enough room around the motor that they shouldn't have had a need for a remote filter. They accomplished nothing other than adding a "weak link" to the system.
yes sir..
I agree. His engine lists the 10w30 as a recommended oil. The owner is thinking his engine is not as smooth as it could be using the 5w30. Switching to a thicker oil may not solve his minor issue, but it is sure worth a try since the heavier weight oils are a listed by GMC as being compatible.
To the Owner, I would try a thicker oil and see if the engine is a little smoother with it. You also asked about conventional or synthetic oil. Conventional oil will work just fine. I believe that Synthetic oil is better and that is what I now use. I switched a truck with 220,000 miles (GMC 1500) to Full Synthetic with no issues. Take a look down inside the oil cap. If it looks pretty clean and you know the truck has had regular oil changes by the previous owner, then switch to a Full Synthetic if your heart desires.
To the Owner, I would try a thicker oil and see if the engine is a little smoother with it. You also asked about conventional or synthetic oil. Conventional oil will work just fine. I believe that Synthetic oil is better and that is what I now use. I switched a truck with 220,000 miles (GMC 1500) to Full Synthetic with no issues. Take a look down inside the oil cap. If it looks pretty clean and you know the truck has had regular oil changes by the previous owner, then switch to a Full Synthetic if your heart desires.
must be a shaky motor, as I run a fleet of 6.0 gas Savana's all with factory oil cooler plumbing.
Never seen one leak across a whole lot of trucks.
Never seen one leak across a whole lot of trucks.
Thanks for all the responses, it took me all morning to actually get on here as now my main computer has decided to be difficult. I will be going over everything looking for any possible leaks in the next few hours, the only thing I can think of off the top of my head is the cloud of white exhaust on first startup. As for fuel economy, I'm kinda baffled by it myself. With the 5w30 in it, I've been averaging an amazing 23mpg in town (I rely on the odometer, not the gas gauge). The thicker oil is tempting, and I very well may try it out just to see. I just wasn't sure if I should be doing much "testing" before driving 700 miles each way 
The previous owner did take VERY good care of it, up until the year before he sold it (it sat parked for a solid year). So I'm not sure if that year could have been hard on the seals. I will also probably change the oil again before the cold temperatures become an issue. Thanks again, I really didn't expect so many responses so quickly.
The previous owner did take VERY good care of it, up until the year before he sold it (it sat parked for a solid year). So I'm not sure if that year could have been hard on the seals. I will also probably change the oil again before the cold temperatures become an issue. Thanks again, I really didn't expect so many responses so quickly.Originally Posted By: BuickGN
To the guys recommending the 5w over the 10w30 for summertime cruising down the freeway, why? I'm honestly curious as to why you make this recommendation.
Because it's what GM recommends first, plus it'll yield slightly better MPG no matter how small and can be ran all summer in through winter Instead of changing it out come winter.
i've had two of these engines and yes 5-30 yields better MPG's,it's all that's needed if engines in sound good shape. BUT.....he can do what he wants,heck if i still had mine she'd have 0-30AFE in the pan.
why do you recommend 10-30? what can it do over a 5,and don't say shearing because a oil can still protect fine with some shearing.
To the guys recommending the 5w over the 10w30 for summertime cruising down the freeway, why? I'm honestly curious as to why you make this recommendation.
Because it's what GM recommends first, plus it'll yield slightly better MPG no matter how small and can be ran all summer in through winter Instead of changing it out come winter.
i've had two of these engines and yes 5-30 yields better MPG's,it's all that's needed if engines in sound good shape. BUT.....he can do what he wants,heck if i still had mine she'd have 0-30AFE in the pan.
why do you recommend 10-30? what can it do over a 5,and don't say shearing because a oil can still protect fine with some shearing.
Originally Posted By: daman
Originally Posted By: BuickGN
To the guys recommending the 5w over the 10w30 for summertime cruising down the freeway, why? I'm honestly curious as to why you make this recommendation.
Because it's what GM recommends first, plus it'll yield slightly better MPG no matter how small and can be ran all summer in through winter Instead of changing it out come winter.
i've had two of these engines and yes 5-30 yields better MPG's,it's all that's needed if engines in sound good shape. BUT.....he can do what he wants,heck if i still had mine she'd have 0-30AFE in the pan.
why do you recommend 10-30? what can it do over a 5,and don't say shearing because a oil can still protect fine with some shearing.
Shearing. Seriously.
Do you really think there's enough of a difference in viscosity between the 5w and 10w during the summer time to make a measurable difference in mpg? He's going to be taking it on a long trip. The number of cold starts is going to be minimal for the amount of miles put on it.
All else being equal, the 10w30 is a more robust, tougher oil. You'll never see the difference in mpg and supposed startup protection in the conditions this is going to be used.
Originally Posted By: BuickGN
To the guys recommending the 5w over the 10w30 for summertime cruising down the freeway, why? I'm honestly curious as to why you make this recommendation.
Because it's what GM recommends first, plus it'll yield slightly better MPG no matter how small and can be ran all summer in through winter Instead of changing it out come winter.
i've had two of these engines and yes 5-30 yields better MPG's,it's all that's needed if engines in sound good shape. BUT.....he can do what he wants,heck if i still had mine she'd have 0-30AFE in the pan.
why do you recommend 10-30? what can it do over a 5,and don't say shearing because a oil can still protect fine with some shearing.
Shearing. Seriously.
Do you really think there's enough of a difference in viscosity between the 5w and 10w during the summer time to make a measurable difference in mpg? He's going to be taking it on a long trip. The number of cold starts is going to be minimal for the amount of miles put on it.
All else being equal, the 10w30 is a more robust, tougher oil. You'll never see the difference in mpg and supposed startup protection in the conditions this is going to be used.
yea yea yea,you forget i had two of these puppy's you can get better with 5w i agree probably small but hey,more robust? hardly, i've beat 5w30 oils before with heat and heavy towing and no failures. Plus the fact he's good through winter vs changing it out.
Originally Posted By: daman
yea yea yea,you forget i had two of these puppy's you can get better with 5w no matter how small,more robust? hardly, i've beat 5w30 oils before with heat and heavy towing and no failures. Plus the fact he's good through winter vs changing it out.
I'm not familiar with the climate where he lives but I doubt the 10w30 would need to be changed for the winter. Why is it that everyone is so careful about the cold end of things with no regard to the hot side.
Sure, you can probably beat on the 5w30 but why not run the 10w30 if it's more robust and there's no downside? Less VIIs to shear and stick piston rings. Higher HTHS. Why not have a larger safety margin? Why don't we all run our cars on a 0w-10 since most people only drive them to 100,000 miles? I'm sure they would just be wearing out at that mileage. Are we just trying to run an oil that will barely make it to the junkyard? I want mine in top shape for it's entire life, not something that has a 20% leakdown rate at 100,000 miles.
yea yea yea,you forget i had two of these puppy's you can get better with 5w no matter how small,more robust? hardly, i've beat 5w30 oils before with heat and heavy towing and no failures. Plus the fact he's good through winter vs changing it out.
I'm not familiar with the climate where he lives but I doubt the 10w30 would need to be changed for the winter. Why is it that everyone is so careful about the cold end of things with no regard to the hot side.
Sure, you can probably beat on the 5w30 but why not run the 10w30 if it's more robust and there's no downside? Less VIIs to shear and stick piston rings. Higher HTHS. Why not have a larger safety margin? Why don't we all run our cars on a 0w-10 since most people only drive them to 100,000 miles? I'm sure they would just be wearing out at that mileage. Are we just trying to run an oil that will barely make it to the junkyard? I want mine in top shape for it's entire life, not something that has a 20% leakdown rate at 100,000 miles.
- Status
Similar threads
