Old Oil/New Oil

I recently inherited a 2003 Tundra with just over 140,000 miles. I have changed all of the fluids and filters, along with many of the suggested maintenance items from this forum, including changing the timing chain. I'm not very mechanically inclined, so this question may be silly, but here goes. Does mixing synthetic oil and regular oil hurt the engine? As the service manual calls for regular oil, this might become an issue in the future as finding regular oil can be challenging. I would appreciate any and all thoughts, suggestions, answers.

 

I would switch to synthetic and stick with it on your next oil change

 

Thank you for your time and suggestions.

 

I wouldn’t put much thought into it. Maybe look for a high-mileage semi-synthetic blend. Any modern oil, changed at the recommended interval, will be fine.

Modern “synthetic” oils are mostly highly refined mineral oils. By 2003, seal material compatibility shouldn’t be an issue. An oil high in PAOs (polyalpha olefins - a true synthetic) may contribute to seal hardening/shrinking at your Tundra’s age.

A high mileage oil would have additional esters (another true synthetic) to act as seal conditioners to mitigate the effects of PAOs.

 

Excellent information. Thank you your time and sharing this information with me.

 

I’ve run full synthetic in my 2000 Tundra since 2005 and 99k miles. I’m at 280k now, no issues. There is no compatibility issues between regular and synth oil

 

5W30 SYN. THIS IS THE WAY

Edit: on a sidenote, the kids in my shop laugh when I talk about how we used to use 10W-30 back in the day. They’ve never heard of it

 

I’ve mixed them on occasion when I was 1/2 quart to a quart low. No it won’t hurt your engine.

I was worried about the gasket saturation problem using Dino oil for the first 100k miles only because I didn’t want to void my extended warranty. For the next 50k miles I switch to Castrol synthetic blend until they jacked up the prices. Now I only use Mobil 1 synthetic with no issues other than the valve cover gasket leaking but I would think everyone has that issue when they’ve got over 200k+ miles.

My older brother experienced the gasket leakage issue when he switched to synthetic on his 95 T100 so he stayed with Dino oil until he got rid of the truck for undercarriage rust so bad, mine looks like a Southern truck in comparison (mine’s pretty bad).

 

Thank you to all for taking the time to respond, answer my questions, and for all of the information you provided.

 

My first vehicle was a 1989 Toyota pickup with the 22RE that had the notorious valve rattle. I ran 20-50 in it until it died.
I have had quite a number of 89-95 pickups and one got so bad before i ran two whole bottles of STP oil treatment in it every oil change till it died. For those that dont know, you gotta put STP oil treatment on the valve cover and ride around a half hour to heat it up just to get it to pour out of the bottle. Its thicker than molasses. It worked wonders BTW.

 

I reckon mentioning using rabbit ears to watch TV would definitely go over their head….and perhaps the instructors

 

Need to bring back old tech in new ways to get people interested….

 

Really? Hmmmm...

 

Imagine trying to explain the difference between the UHF and VHF knob…

Or how, for too many years, TVs doubled as furniture.

 

Yup, good ol motor honey

 

You have to change the oil? What??

https://sl.bing.net/hJetHkhgwXk

LOL

 

You forgot to post a video of that cat's car when it finally got an oil change.

https://www.youtube.com/watch?v=MskJaTr2uho​

 

I once bought an old Pontiac for parts and when I removed the valve cover.......the plug of oil inside was in the exact shape of the inside of the valve cover.

I'm assuming----never changed the oil. Sad, it was Pontiac's top line model for 1976.