Low oil pressure after oil change

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Heffenoche

Heffenoche

Joined
Dec 22, 2003
Threads
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514
Location
VA
I purchased my FZJ80 about six months ago with a fresh oil change (10w-30) and aftermarket filter. The oil pressure gauge read high at start up, between the two lines after warm up while driving, and would sit at the 1/3 line at idle.

I just changed the oil with 10w-30 and Toyota filter (the good one). The pressure gauge reads the same except sometimes at idle. I was stuck in traffic during our 10” rain storm and the gauge would drop to half way between low and 1/3 at idle, then when the ac would kick the rpms up the gauge would go up to a little above 1/3. I know the Toyota gauge is notorious for being inaccurate but the drop at idle has me concerned since it appears to happen after the oil change. The oil level is not low.

How concerned should I be? I guess my next step should be to check the pressure with a manual gauge. I’ve never done this, how difficult is this and what am I looking to spend on the test gauge?

Good thing is my sun roof didn’t leak a drop.
 
Heffen-what oil are you running? First change I ever did to amSPOIL synthetic scared the crapola out of me when I saw how low the pressure was. The synth just read lower most of the time.
 
I'll give a short explenation, but you can search for more info that I have posted in the past on the subject.

There are two things going on here:

1) 30 weight is not a specific thickness at operating tempurature, but in fact a range of thickness at operating temp. 30 weight can be from 9.3-12.5 cst @ 100c. Mobil 1 30 weights tend to run about 9.8, while castrol GTX is about 12. The change you see can simply be from changing brands, where one oil is slightly heavier than the other.

2) Depending on how long the oil was in use, the old oil could have thickened out of grade (i.e. become a 40 weight at operating tempurature). What happens is that as an oil additives package is used up, oxidative thickining occures which will cause the oil to thicken. Usually this is not a concern, but could very well happen over a 5000 mile oil change with a cheap fleet oil (wolf's head, etc). Given you didn't change the oil yourself it is likely the place that did it used a cheap fleet mineral oil.

The bottom line is that the oil pressure gauge at idle being halfway between the bottom and the first hash mark is fine. I would recommend that you consider changing to Mobil 1 0w-40 or as a cheaper alternative from Walmart, Shell Rotella T Synth 5w-40 at your next change (5000 miles for mineral, 7500 for synthetic are fine). If you want to use mineral oil, I would recommend Chevron 15w-40 Delo for summer, and Delo 10w-30 for use bellow 40f. If you live in a really cold climate (less than 0f starts) and use mineral, sub the 10w-30 with a 5w-30 for winter use.

Cary
 
cary said:
I'll give a short explenation, but you can search for more info that I have posted in the past on the subject.

There are two things going on here:

1) 30 weight is not a specific thickness at operating tempurature, but in fact a range of thickness at operating temp. 30 weight can be from 9.3-12.5 cst @ 100c. Mobil 1 30 weights tend to run about 9.8, while castrol GTX is about 12. The change you see can simply be from changing brands, where one oil is slightly heavier than the other.

2) Depending on how long the oil was in use, the old oil could have thickened out of grade (i.e. become a 40 weight at operating tempurature). What happens is that as an oil additives package is used up, oxidative thickining occures which will cause the oil to thicken. Usually this is not a concern, but could very well happen over a 5000 mile oil change with a cheap fleet oil (wolf's head, etc). Given you didn't change the oil yourself it is likely the place that did it used a cheap fleet mineral oil.

The bottom line is that the oil pressure gauge at idle being halfway between the bottom and the first hash mark is fine. I would recommend that you consider changing to Mobil 1 0w-40 or as a cheaper alternative from Walmart, Shell Rotella T Synth 5w-40 at your next change (5000 miles for mineral, 7500 for synthetic are fine). If you want to use mineral oil, I would recommend Chevron 15w-40 Delo for summer, and Delo 10w-30 for use bellow 40f. If you live in a really cold climate (less than 0f starts) and use mineral, sub the 10w-30 with a 5w-30 for winter use.

Cary
Click to expand...

I believe that Cary is the local oil experct around here, but here's my opinion.

I've done 5 oild changes in the last 10,000 miles to clean whatever the PO left in... crud included.

Please remember that my experiments are based on a engine with 233,000 miles at the time. As a guage reference we'll start with the bottom line of the oil pressure guage at line 1 and work our way north to line 4.

When I started (no oil change in who knows how long) idle barely @ line 1 and 70 mph @ ?

First oil change Mobil 15-40 delvac? idle line 2 - 70 mph 3.

Second oil change Shell Rotella 15- 40 same as Mobile, but I just like it better.

Third oil change Shell Rotella sin 0 - 40 idle 2/3 of line 2 - 70 mph 4/3 of line 3, oil seaping and burning oil at 1 qt per 1500 miles.

Forth oil change Mobile 1 sin 15-50 idle line 2 - 70 mph 3.25 above line 3, oil seeping less than Shell.

Fifth same as third and my final solution.

When I fisrt started this oil adventure I was concerned about how low the oil pressure was so I ask an Toyota mech and he said that at idle all you really need is 7psi or barely above line 1.

I don't know if this helps or applys to your situation (200,000 miles) but Shell Rotella 15-40 @ $6.50 a gallon works for me, no seepage and no burning.

Good luck.
 
I replace with Castral GTX 10w-30. I'm not sure of the other brand but it had no more than 3,500 miles at around 7 or 8 month on the interval. Sounds like I'm ok but I may change brands of oil. Thanks for the help and peace of mind.
 
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