10 years on 20w50 conventional oil now switching to 5w30 fully syn

[Ziyad28]

Hello guys my car has been running on 20w50 conventional oil for almost 10 years, its 08 model with the V8 it has around 180k mils now.
before anyone get mad this is my father car and he chose this type of oil due to our hot climate in KSA. I notice lately that it has a rough idle during a cold start. so I decided to change the oil to 5w30 full syn. my first impressions was the engine ran way smother and I don't need to push the gas paddle that much to accelerate.
should I stay on 5w30 syn or not ?
I'm worried that it may cause future engine leak

thank you

 

[94Eddie]

I don't think changing to 10W30 synthetic will cause any issues. One sign would be if is starts burning oil (i.e. it needs topped up in between oil changes) which might mean it has suffered wear in the piston rings and/or cylinder walls. I can see where performance might be better since the engine isn't experiencing the drag on moving parts from a thicker oil. This is one reason manufacturers have gone to using thinner oil to improve mpg. Also, the VVT solenoids, oil passages etc. were designed to use a thinner oil so you might be seeing improvements associated with these parts/components running within spec from using 10W30. If it isn't burning oil then I think you will be fine switching to 10W30.

 

[Fix4Dirt]

Hello guys my car has been running on 20w50 conventional oil for almost 10 years, its 08 model with the V8 it has around 180k mils now.
before anyone get mad this is my father car and he chose this type of oil due to our hot climate in KSA. I notice lately that it has a rough idle during a cold start. so I decided to change the oil to 5w30 full syn. my first impressions was the engine ran way smother and I don't need to push the gas paddle that much to accelerate.
should I stay on 5w30 syn or not ?
I'm worried that it may cause future engine leak

thank you

i think staying with 5/30 will do fine, especially with the thin passages in the motor. 20w50 is real thick! it should frun slightly smoother VVT and what not, and might have more power, i wouldnt be surprised. also better fuel economy. i think staying on 5/30 is fine however, it was designed so imo no more/less likely to leak than another 3v imo, unless of course there is a leak already which was sealed due to the oil being so thick, so basically thick oil hiding a leak. however if there is no underlying leak, i think youre good.

 

[J_C]

If continuing to use the same oil and suddenly some problem, it makes no sense to change the oil and pretend that fixes it. You have some other problem.

My first two guesses are you need new spark plugs, or have a vac leak, or maybe you just need the IAC cleaned/replaced.

No, rough idle is not cured by dropping to a lower oil viscosity.

If the engine doesn't have excessive wear, 5W30 is not an unreasonable choice of viscosity, but you are fixated on the wrong thing.

Yes a lower viscosity oil may leak easier but it is beside the point which is this isn't relevant to finding the fault.

Just no, abandon all thoughts on this matter and troubleshoot the rough idle symptom the normal way.

 

[Ziyad28]

If continuing to use the same oil and suddenly some problem, it makes no sense to change the oil and pretend that fixes it. You have some other problem.

My first two guesses are you need new spark plugs, or have a vac leak, or maybe you just need the IAC cleaned/replaced.

No, rough idle is not cured by dropping to a lower oil viscosity.

If the engine doesn't have excessive wear, 5W30 is not an unreasonable choice of viscosity, but you are fixated on the wrong thing.

Yes a lower viscosity oil may leak easier but it is beside the point which is this isn't relevant to finding the fault.

Just no, abandon all thoughts on this matter and troubleshoot the rough idle symptom the normal way.

My first two guesses are you need new spark plugs, or have a vac leak, or maybe you just need the IAC cleaned/replaced.

Thanks for all replies guys very helpful, @ J-C: you'r actually right I do need to change spark plugs , also for IAC I don't remember cleaning it before. I do have scanning tool "Think diag" I scan the car from time to time for any codes I recall one time it said misfire detected first 1000rpm at start code P0316-FF

 

[94Eddie]

Definitely change the spark plugs if this hasn't been done in a while or ever. I changed mine at 120k miles and the center electrodes were worn so badly that the gap was twice as wide is specified. I noticed a big difference in how the engine ran and this solved a cold starting problem that I was trying to find a cause for. The engine runs smoother, accelerates better and gas mileage has improved by 1-2 mpg. You also should consider replacing the VVT solenoids since these can go bad and affect the cam timing. While you have the valve covers off check the roller followers for wear and replace any bad ones, if needed. Also, it wouldn't hurt to change all the fluids if this hasn't been done in a while. This would be brake fluid, coolant, transmission fluid (and filter), rear differential fluid, front differential and transfer case fluids (if it is 4WD) and power steering fluid. It is important to drain and refill the transmission fluid every 50k miles. The 6R60 transmissions can have issues if the fluid isn't changed regularly.

 

[94Eddie]

One thing I need to add regarding the spark plugs is the ones in the 2006-2008 4.6L 3V are two piece designs that have a tendency to break off when they are extracted. There is a procedure to follow to reduce the odds of this happening. You can find a lot of YouTube videos that cover how to remove the plugs. If one does break off there is a special tool that will extract the broken tip from the head. It is called The Lisle 65700 Broken Plug Remover Kit for Ford 3V Engines. You might want to get one before you remove the plugs if you can't deal with the vehicle being inoperable until you would have one shipped to you.