Mobil1 15w50 experiment

Joined
Dec 4, 2013
Messages
774
Location
Maryland
Gonna do a long term experiment on mobile1 15w50. Temp range where I live goes from -10f to 100f. Gonna use 2 vehicles. A 2001 k1500 4.8l automatic. 205k on it. No cats. No egr. No knock detector. Known cam lobe wear. I forget which one but it was for cyl 7 or 8. Absolute beater of a truck. Was running t6 5w40. 1st impressions of the 15w50 is engine is quieter. But feels more sluggish. According to the horrible gm guages oil pressure has risen about 5 to 10 psi. Idles at 40 to 50. 60+ running down the road. Also about a 5deg rise in engine temp. Running about 180 on a 160 thermostat. 2nd vehicle is a 2008 Toyota yaris 1.5 automatic. 195k miles no catalytics. Was the wife's car and has been abused. Haven't driven that yet since the change from t6 5w40. Wife currently drives a 2011 nissan cube. But I'm not brave enough to switch that from t6 to 15w50 with it being our nice car and with winter coming. Learned alot on bitog and enjoy reading people's posts

Maybe back in the day thicker oils were better to a certain extent, but you said the engine feels sluggish and there is a rise in temp. Your engine is working harder to push around thicker oil so that is why you are seeing the rise in engine temps.

Back in the 80;s I was running 20W-50 during the summer and the coolant temp gauge was pegged at 220 with a mechanical fan. I then went to 10W-30 and the temp gauge went back down to about 195 or so. Was my temp gauge accurate, who knows, but I wish I had an infrared gun back then to take some temp readings.

Good Luck
 
Joined
Mar 19, 2022
Messages
249
I'm surprised no one has mentioned this, but the "horrible GM gauges" likely include a dummy gauge for the oil pressure, so whatever readings you're getting from that are probably not worth a whole lot of your attention.

I know Mazda started using dummy gauges back in the early 90s, I'd be surprised if GM wasn't using them in 01.

I have coolant temp, oil pressure, and voltage gauges on my 16 Silverado, and none of them relay accurate information.
Only Ford based Mazdas use dummy gauges....just like Ford has done since the 80s. GM actually has a pressure sender and not a pressure switch like Ford.
 
Joined
Jul 5, 2019
Messages
483
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STL, MO
Only Ford based Mazdas use dummy gauges....just like Ford has done since the 80s. GM actually has a pressure sender and not a pressure switch like Ford.
My experience was in a 99 Mazda Miata, which was not at all Ford based. From my understanding, Mazda went to the dummy gauge in 94, when they switched from the B6 to the BP engine (1.6L to 1.8L). This is at least for the Miata. I can't speak for the rest of the lineup.
 
Joined
Jul 5, 2019
Messages
483
Location
STL, MO
My experience was in a 99 Mazda Miata, which was not at all Ford based. From my understanding, Mazda went to the dummy gauge in 94, when they switched from the B6 to the BP engine (1.6L to 1.8L). This is at least for the Miata. I can't speak for the rest of the lineup.
Also, I currently own a GM, and I also run a OBD gauge. Engine temp from what the ECM reads and what the gauge reads are wildly different. Same for voltage. Oil pressure gauge doesn't read anything different between cold and hot oil, so that reading is clearly BS as well. It may or may not have a pressure sensor, IDK, all I know is the reading it displays is completely erroneous. (2016 Silverado 2500 6.0L)
 

Imowgrass

Thread starter
Joined
Oct 5, 2022
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14
Update on the 15w50. Been running the 08 yaris mostly this week. First gas fill up on only 15w50 was 5.8 gals for 208 miles. So 35 mpg. Zero drop on mpg on this oil. This includes longer warmup time. Also the cat was deleted right before the switch and the 2nd o2 sensor along with it. One negative is that I was running late for work one day and didn't let the car warm up and it did not seem happy about it. It felt like a start and go in the 20f range but it was in the 40fs
 
Joined
Oct 4, 2012
Messages
1,342
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Rabbit Creek, Alaska
There are thousands of people who run conventional 15w40 in diesel trucks here in Alaska year round. I predict nothing will happen yet this thread will be filled with anecdotes and "feelings" that won't be able to be measured. Then the "findings" will be misconstrued and will be espoused as gospel. Catless :rolleyes: Yaris running 15w50. Riveting stuff.
 
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FCD

Joined
Oct 22, 2015
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3,904
Location
Mallorca, Balearic Islands, Spain
I've started many a engine in below freezing temps with 20W-50 Dino in the sump, sometimes the op gauge would be pegged right at the top for a bit but otherwise nothing happened and they didn't blow up, which we know is the official standard of BITOG 🤪
 
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