1993 ls400 oil pressure
 

So I bought this lexus a couple months ago and it has generally been rock solid....right up until my idiot room mate decided to get the oil changed at wally world. I drove it afterwords and after less than 100 miles the low oil pressure light came on. I was pretty pissed needless to say. Anyways, I granny drove it to the gas station with the oil light flickering at me and found it to be a quart and a half low, so I topped it off but ever since then I have been running into oil pressure issues. It seems to me that the oil is getting to warm and losing viscosity. They (supposedly) put 10-30 castrol high mileage in it, I did add a quart of Lucas oil stabilizer to it but it doesn't seem to help, if anything it seems to heat up the oil faster than before. I am wondering if it had synthetic in it and the switch to conventional is what is causing the problem, or if the thicker oil is somehow causing it to heat up faster. I am a bit lost. Engine has plenty of power, doesn't make any terrible noises, doesn't leak, but seems to burn a bit of oil slowly(no smoke, but the oil needs topped up every couple weeks) Any thoughts?

You just never know what under paid little trained people that have zero mechanical aptitude could be adding to any of the various reservoirs on a car. Maybe water in the wrong place, maybe brake fluid in the wrong place and the list goes on. Maybe it was goof with the customers day, cause it was the day to quit, ya just had enough of the boss and stupid cars.

What are the chances of the motor being damaged in a serious way? I will be changing the oil this weekend with a good synthetic and putting on an uber oil filter. (used to build them for work)

I think these call for 5w-30 and these cars take 5 and a half quarts from what I've read.

And why does the room mate have the key and is allowed to drive the car? Pretty much no one drives my car or uses my tooth brush and I would never take a car to a jiffy lube type joint for an oil change too many horror stories.

I have 7 cars and had lent the car to my room mate because her escort threw a timing belt. I have had pretty good experience at Jiffy Lube/Grease Monkey personally. And I told her to have the oil changed at anywhere besides Walmart.......If the oil change doesn't fix the problem I am probably going to tell her she needs to find me a new Lexus 400 of some kind (gs,ls,sc, don't care). I bought the car for 500$ (interior is less than great, paint is effectively gone) and I only bought it for engine swap potential. Will probably be doing a 10-30 full synthetic for it. The oil filter that I have for it is a re-usable cartridge style (blows any parts store brand out of the water)

1.5 qts low?

I don't know about your car, but my '91 has a capacity of 5.6 qts, and I have twice found that when the oil level gets low enough that it would be on the low line of the dipstick when checked properly, the oil LEVEL light will start to flicker at highway speed and temp. This happens and the oil PRESSURE light never comes on except of course at startup.

So of course, those two times the oil level light came on I checked it carefully and was very impressed at the accuracy of it, and added a quart and went on my way. But I think that level sensor, if working properly, would prevent me from ever being below the Low line, and definitely never 1.5 qts below the High line.

So anyway, I'd recommend making sure you're watching both the oil pressure and the oil level lights. I doubt 10w30 would cause any problem, but as others have said, you never know what they really put in there.

What happened was the oil pressure light came on first, then the low oil light was coming on during right hand turns.

So low level and pressure. Certainly something within the capabilities of Walmart (or any low cost oil changer). They could have used 0W20 or something that might give low pressure and 4 qts - your car doesn't look like a 2014 Honda Civic does it? ;-)

I'd just redo the oil change myself and expect that to fix things. Good luck.

Taking it through emissions was hilarious to watch, they ran over their block 3 times before they realized it was rwd.

So if someone at emissions gets in and operates your car, and it breaks does that mean they get to pay for it?

I honestly don't know, they may have scuffed a quarter panel, but seeing as i originally bought it as an engine donor, I wasn't concerned about it. Car still drives well with no noises in the suspension, tracks straight, and doesn't wear tires unevenly. Chalk it up to a funny story.