Performance Loss, Strong oil burning smell, great gas mileage

[Moist]

I don't usually drive her hard enough anymore to notice any performance loss. I know she's kicking around 185 ish for horsepower (as of 3 or so years ago)
Recently though after an oil change I'm noticing a very strong oil burning smell, and have to give a more pedal than usual for things like merging on the interstate. She really doesn't want to go above 4K, and takes her sweet time to move forward.
Oil level is full, but not overfilled. There's no knocking (except for maybe 5 seconds worth on a 30 degree start), nor any CEL/Warning lights. Oil is getting dark already after 1,500 miles.

For some reason too I am averaging 22ish mpg from the motor interstate. The burning smell fills the cabin when the windows are open, but MAN that mileage. The display panel is off by about 3-4 mpg, but from my estimations I am averaging 20-23 MPG.

This whole thing is worrying me. Its not the worst thing ever, but it really feels like something is wrong but I just don't know what. Especially since she feels better than ever and yet struggles to get up to & hold 70 sometimes.

She's a 2003 4runner V8 SR5 4WD. She also exclusively drives the interstate, and holds 2K at 70 for the entire daily drive.

 

[SurferUK]

I wonder if your PCV valve has failed open. Just a hunch but I once started a car with the PCV removed and it ran like a bag of crap just ticking over, and it might explain the oil smell too.

I can't think of anything else that covers both, a failed rocker cover gasket for example wouldn't cause bad performance just a hot oil smell.

You didn't mention leaks/drips so I assume it's all still oil tight.

 

[Moist]

I wonder if your PCV valve has failed open. Just a hunch but I once started a car with the PCV removed and it ran like a bag of crap just ticking over, and it might explain the oil smell too.

I can't think of anything else that covers both, a failed rocker cover gasket for example wouldn't cause bad performance just a hot oil smell.

You didn't mention leaks/drips so I assume it's all still oil tight.

eeeeeeeehhhhhh sorta oil tight. Bottom end is oil tight with no leaks. Valve covers were leaking same thing with the timing cover, but they've gummed up since then and the oil leakage has slowed to a seep.
It's burning the oil from the exhaust. There's a thick layer of burnt oil on the rear bumper.

 

[SurferUK]

eeeeeeeehhhhhh sorta oil tight. Bottom end is oil tight with no leaks. Valve covers were leaking same thing with the timing cover, but they've gummed up since then and the oil leakage has slowed to a seep.
It's burning the oil from the exhaust. There's a thick layer of burnt oil on the rear bumper.

A failed PCV valve could still cause that I think, if it was failed shut it would over-pressurise the crankcase, but I'm actually wondered if it could be something as simple as oil that's too thin. The timing is too closely correlated to start thinking of too many mechanical issues.

I don't know if a failed bypass valve on the filter would cause oil burning but it might be worth looking up and also checking it's done up tight enough (Not too tight), and that they haven't left the old gasket on there by accident.

I don't know the V8 layout but if you haven't verified the smoke is definitively coming out of the exhaust, it could be oil dripping onto it, then burning!

 

[Moist]

A failed PCV valve could still cause that I think, if it was failed shut it would over-pressurise the crankcase, but I'm actually wondered if it could be something as simple as oil that's too thin. The timing is too closely correlated to start thinking of too many mechanical issues.

I don't know if a failed bypass valve on the filter would cause oil burning but it might be worth looking up and also checking it's done up tight enough (Not too tight), and that they haven't left the old gasket on there by accident.

I don't know the V8 layout but if you haven't verified the smoke is definitively coming out of the exhaust, it could be oil dripping onto it, then burning!

I will check the PCV valve and bypass valve as soon as I ain't sick. I'm using pennzoil 5W-30, and an OEM V8 filter that I bought from the dealership.

The oil is 100% being burnt out the exhaust. There's a thick soot over the rear bumper, and the exhaust burns blueish smoke especially on startup.

She isn't running hot, knocking, misfiring, really anything. It's started whining but aside from the noticeable performance loss seems alright. (Except for the severe power loss at 4K RPM)

I wonder if it's several things finally rearing their head. I will check the PCV valve and inspect the oil filter again. thank you!

 

[SurferUK]

I will check the PCV valve and bypass valve as soon as I ain't sick. I'm using pennzoil 5W-30, and an OEM V8 filter that I bought from the dealership.

The oil is 100% being burnt out the exhaust. There's a thick soot over the rear bumper, and the exhaust burns blueish smoke especially on startup.

She isn't running hot, knocking, misfiring, really anything. It's started whining but aside from the noticeable performance loss seems alright. (Except for the severe power loss at 4K RPM)

I wonder if it's several things finally rearing their head. I will check the PCV valve and inspect the oil filter again. thank you!

I had a Suzuki that puffed blue smoke on startup, I think it was the valve stem seals. I never worked out how it had happened (It would have been doing it with the previous owner too) or how I got unlucky, or spent any money on it - I just kept an eye on the oil level when I realise it was a 'burner'!

I only mention it as after looking into it, it didn't seem like the sort of thing that just happens one day.

Do you ever give it an 'Italian tune up'? I've got older engines that are driven gently through our MOT emissions tests by putting a tank of premium fuel and whatever random fuel system cleaner was cheapest in the tank, and absolutely thrashing them for an hour. To the redline in every gear every time, but also using engine braking, that's the important part. It's like when we give our backs and legs a really good stretch.

I suppose you could do a compression test and that would pretty much tell you definitively. You could check the condition of the spark plugs at the same time.

Do let me know what you find though, I am intruiged!

 

[Moist]

I had a Suzuki that puffed blue smoke on startup, I think it was the valve stem seals. I never worked out how it had happened (It would have been doing it with the previous owner too) or how I got unlucky, or spent any money on it - I just kept an eye on the oil level when I realise it was a 'burner'!

I only mention it as after looking into it, it didn't seem like the sort of thing that just happens one day.

Do you ever give it an 'Italian tune up'? I've got older engines that are driven gently through our MOT emissions tests by putting a tank of premium fuel and whatever random fuel system cleaner was cheapest in the tank, and absolutely thrashing them for an hour. To the redline in every gear every time, but also using engine braking, that's the important part. It's like when we give our backs and legs a really good stretch.

I suppose you could do a compression test and that would pretty much tell you definitively. You could check the condition of the spark plugs at the same time.

Do let me know what you find though, I am intruiged!

Italian tune up done.
Flat out she'll do 0-60 in about 11.52 seconds with a quarter tank. At 4000 RPM on certain low grade fuels she'll lose most power over 4K and start shaking bad.
Coolant temp rises noticeably with RPM, but I've known my radiator is bad since I got the car. Also noticed a new coolant leak.
Plugs are new-ish and mostly fine but are a bit dark.
Was a lot of fun to get this thing up and going, was running a little bit better near the end of the tune up. Still sluggish and not happy with interstate speeds most of the time but feels slightly better.

-------I don't have the tools for these so I had a friend look at it while I was in classes-------:
Compression is overall fine. Lower than factory spec but okay. Interestingly I was told on a cold start some of the cylinders were really low. I was also told oil is most likely advancing through piston rings on cold start.
Oil pressure is apparently much higher than expected, but isn't worryingly high.
I wasn't given exact numbers except for the low compression which had the cylinders sitting around 150-ish. However when hot, was more about 180.

Additionally oil is much darker than normal. Going to get oil sample done when I change it in a few weeks. This isn't due to oil dilution/fuel contamination as this car only drives interstate at the moment, and the conditions are not right for significant oil dilution.

Otherwise aside from some base level things I haven't really looked at it. To be honest I don't know how much I trust his compression tests either. He said a lot of weird things and I wasn't there for any of it. (Couldn't tell me what cylinders were low.)

The PCV valve is most likely failed. Will replace since it's a 12$ part and I'd like an excuse to drag my friends over to laugh at this thing. (A tradition) It looks fine from the outside, but peace of mind is a lovely thing.
Might also be some pressure relief valves going bad. I saw that on the forums too.

 

[SurferUK]

Still nothing solid then...once you change the PCV valve, even though you don't have a EML I think it's worth finding someone with a copy of Techstream and reading some values. I would but there is an ocean in the way.

Just out of interest, when was the battery last changed and can you do a voltage reading of it?

 

[SocalSam]

Some of the symptoms fit oil overfill.

Attention Required! | Cloudflare

The link is to a JD Power article called "What Happens When You Put Too Much Oil In Your Car. Suggest you google and pull up article that way. Not sure why out forum is showing link as it does.

 

[Moist]

Still nothing solid then...once you change the PCV valve, even though you don't have a EML I think it's worth finding someone with a copy of Techstream and reading some values. I would but there is an ocean in the way.

Just out of interest, when was the battery last changed and can you do a voltage reading of it?

The battery is only two years old. I might be able to test voltage, I feel like that's a tool I have.

 

[Moist]

Some of the symptoms fit oil overfill.

Attention Required! | Cloudflare

The link is to a JD Power article called "What Happens When You Put Too Much Oil In Your Car. Suggest you google and pull up article that way. Not sure why out forum is showing link as it does.

I see, I will check oil level again. It has been right at the full line since the last oil change, didn't think it was bad because it was still in the lines. Those symptoms are eerily close. (Well minus the misfire it only did that once)
Will report back later! Thank you!

 

[SurferUK]

The battery is only two years old. I might be able to test voltage, I feel like that's a tool I have.

I just mentioned it as an unstable and/or low battery voltage can cause all manner of weird symptoms and you can end up chasing your own tail!

 

[SocalSam]

I see, I will check oil level again. It has been right at the full line since the last oil change, didn't think it was bad because it was still in the lines. Those symptoms are eerily close. (Well minus the misfire it only did that once)
Will report back later! Thank you!

I have only one year with my V6 and was caught out by how tricky it is to read the oil dipstick. My vacuum pump pulled out 4 quarts through the dipstick tube. Since capacity is 5.5 quarts, I can see how easy it would be to dump in 5.5 quarts which would result in overfill condition.

 

[SurferUK]

I have only one year with my V6 and was caught out by how tricky it is to read the oil dipstick. My vacuum pump pulled out 4 quarts through the dipstick tube. Since capacity is 5.5 quarts, I can see how easy it would be to dump in 5.5 quarts which would result in overfill condition.

The "dipstick issue" on these is like nothing I have ever seen. I don't think I've ever owned a vehicle where it's so hard to get an accurate reading of the oil level. Diesels being the easiest as it's black again in 50 miles.

Same with my 2TR-FE as the dearly departed 1GR-FE.

 

[Moist]

To add onto this it says it's full at the top bar. I'm going to assume it's overfilled then and remove some oil to get the reading lower. I think I'm just gonna run a tube down there and try and pump a little out. Unless there is an easier way that doesn't involve dumping my oil pan into a catch container. (she's sitting in a public parking garage atm.)
Everywhere i saw said it was 6.6 quarts the v8 took.
I wonder if they make aftermarket stuff to solve the hard readings.

 

[AuSeeker]

To add onto this it says it's full at the top bar. I'm going to assume it's overfilled then and remove some oil to get the reading lower. I think I'm just gonna run a tube down there and try and pump a little out. Unless there is an easier way that doesn't involve dumping my oil pan into a catch container. (she's sitting in a public parking garage atm.)
Everywhere i saw said it was 6.6 quarts the v8 took.
I wonder if they make aftermarket stuff to solve the hard readings.

Did you check both sides of the dipstick, on mine it will read higher on one side?

Also on my 2004 V8 I have always put in 6 1/2 quarts to get it to the full mark, after draining and a new filter.

 

[Moist]

Did you check both sides of the dipstick, on mine it will read higher on one side?

Also on my 2004 V8 I have always put in 6 1/2 quarts to get it to the full mark, after draining and a new filter.

Both sides? Mine only has dots on one side if I'm not mistaken. I'll check again later, but I am almost certain the other side is smooth. Otherwise there is a thin trail leading up almost the whole length of the stick's edge of lighter colored oil.
The main reading is consistent on both sides since the oil is so dark its easy to tell.

 

[AuSeeker]

Both sides? Mine only has dots on one side if I'm not mistaken. I'll check again later, but I am almost certain the other side is smooth. Otherwise there is a thin trail leading up almost the whole length of the stick's edge of lighter colored oil.
The main reading is consistent on both sides since the oil is so dark its easy to tell.

I don't recall if it has maks on both side but I always compare the oil on the stick on both sides and it always is a little higher on one side.

 

[SocalSam]

To add onto this it says it's full at the top bar. I'm going to assume it's overfilled then and remove some oil to get the reading lower. I think I'm just gonna run a tube down there and try and pump a little out. Unless there is an easier way that doesn't involve dumping my oil pan into a catch container. (she's sitting in a public parking garage atm.)
Everywhere i saw said it was 6.6 quarts the v8 took.
I wonder if they make aftermarket stuff to solve the hard readings.

Be careful, never assume when it comes to oil. From consulting with members who know what they are doing (not me), the best method is to read dip stick first thing in the morning. First reading is the best. Second reading will pull oil up the tube and stick which will result in a higher reading.