When my local store was out of Mobil 1, I bought some Pennzoil Ultra for my 02 UL. I use the 5 quart container and add about a 1/2 of quart. Since I have a fresh quart of Mobil 1, my question is am I doing any harm by adding a half quart of Mobil 1 to the 5 quarts of Pennzoil?

It may be a dumb question but I was taught that the only dumb question is the one not asked.

Not sure if Ultra is syn?
If you are this **** your car will last a long time, no worries there are blended oils all day long syn to syn is fine on occasion if needed.

You're fine.. there are synthetic blends which are 50/50 or 40/60 so you're fine mixing. It's not like the two won't mix and the 1/2 qt Mobil 1 will float to top.

there are people who mix their own oils on purpose.. kinda like a cocktail drug..

No worries on mixing them.

synthetic mixed with synthetic or syn mixed with conventional.... neither will do you any harm

I'm a little confused. You are putting 5 1/2 quarts of oil in your 430?
Page 343 of my 2002 owner's manual states oil capacity with filter change as being 4.8 quarts.

5.5 for drain and fill oil change with filter is correct for LS430 (at least for my 2006)

Lexus must have changed the pan capacity,
01-03 was less than 5qt while 04-06 was 5.5.

I wish mfrs. would make it an even no. of quarts. These shops seldom seem to get it right, often overfill.
Lexus dealer apoarently put 5 qts. in my '02 LS430, because it reads above the full mark. Manual lists 4.8 quarts.
.2 quart is less than 1 cup full.

Ahh... .2 qts don't sweat it. When use to get the full jug, I would go with 5 qts and it went to middle of hash, which was fine with me. Now I get Costco case, so I put the 5.5.

Lexus owner's manual specifically says not to overfill. It's aggravating when technicians don't follow factory recommendations.

I am aware of this contradiction. The '02 owners manual on pg 343 says 4.8 qts w/ fliter change. When you put in that amount, the dipstick shows a little more than a half quart low. In addition, my recollection is that my '97 LS took more than 4.8.

I've asked a few dealer senior service techs and parts department managers. They all say the true capacity at around 5.5 to 5.6 quarts (a little more if you let it drain for a long period of time). The explanation is always the same, the owners manual capacity is incorrect and attribute this to a misprint. In addition, they say the manual is only an approximate amount. You have to check and fill according to the dipstick.

That said, I pour in the 5 qt jug, add a half of a quart and the level is always at full with 5.5 qts. Thank you for your responses.

Drain the penzoil out asap, they are prone to cause sludge in engines, google it and you will see

Even the Pennzoil Synthetic?