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Discussion Starter · #1 ·
The oil life gauge has gone off on my truck, at about 7500 miles.

I'm trying to decide what is a reasonable amount of miles/hours, because I'm guessing it has gone off too early, given that I had it changed to full synthetic diesel engine oil last time. Perhaps they forgot to reset it (next time I'll reset it myself), since the warning hadn't gone off for the first change yet.

I haven't done too much idling or anything, mostly highway miles, actually.

Any suggestions of a normal oil change interval for full synthetic in the Texas heat?

Thanks!
 

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If you really want to know where you stand you will need to have a Used Oil Analysis (UOA) performed on the oil. However, 7500 miles is pretty good. What kind of driving are you doing? Lots of highway miles? What about towing? If all of your emissions equipment is still in place, you will need to consider fuel dilution as part of the reason you will need to change the oil (e.g. regens introduce fuel dilution, but highway miles can help reduce the dilution due to less regens). The new diesels (post 2007) with the emissions systems they have do not lend themselves to extended OCIs. Texas heat is not really anything to be overly concerned about. I saw some really high temperatures in the mountains in SoCal and Nevada and my UOA came back normal. I was running Mobil Delvac 1 ESP 5W-40 at the time.
 

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The oil life monitor determines the oil change interval based on mileage, driving, temperature and stuff like that. It doesn't actually know what condition the oil is in or the type of oil you are using. I usually get the message every 7,500 miles and average ~10K a year. I do short trip my truck a bit but try to take it on a longer drive at least once a week.
 

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Discussion Starter · #5 ·
If you really want to know where you stand you will need to have a Used Oil Analysis (UOA) performed on the oil. However, 7500 miles is pretty good. What kind of driving are you doing? Lots of highway miles? What about towing? If all of your emissions equipment is still in place, you will need to consider fuel dilution as part of the reason you will need to change the oil (e.g. regens introduce fuel dilution, but highway miles can help reduce the dilution due to less regens). The new diesels (post 2007) with the emissions systems they have do not lend themselves to extended OCIs. Texas heat is not really anything to be overly concerned about. I saw some really high temperatures in the mountains in SoCal and Nevada and my UOA came back normal. I was running Mobil Delvac 1 ESP 5W-40 at the time.
Thanks, next time I have the indicator come on, I might get an analysis done. I did occasionally tow a trailer/smoker during the life of that oil, so I suppose that adds to it. I definitely do more highway miles, because we use that truck primarily for visiting family out of town. In town, I have a car, and a smaller F150.

The oil life monitor determines the oil change interval based on mileage, driving, temperature and stuff like that. It doesn't actually know what condition the oil is in or the type of oil you are using. I usually get the message every 7,500 miles and average ~10K a year. I do short trip my truck a bit but try to take it on a longer drive at least once a week.
I appreciate for the confirmation that it indeed is smarter than just a simple mileage indicator. I have a 2011 Fiesta in which it is just 10k miles, no intelligence whatsoever. Of course, Ford doesn't recommend 10k miles in Texas, so it's worthless. When I searched the forum, I found differing accounts of how the oil life was calculated.

I went ahead and had them do the oil change, with the understanding that it doesn't seem entirely too soon. I have never done synthetic before, except in that Fiesta.
 

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I am no expert in any shape form or fashion so the following are just my thoughts and experiences. Way back when, Dad taught me, if using synthetic oil, 'change the filter and add a quart'. Dad used that model on a 1970 Buick and it lasted for 20 plus years - to my knowledge it never had a 'full' oil change except when he switched out the manufacturers oil for Mobile 1 synthetic. Then along came PCV (positive crankcase ventilation) and then EGR, and now our regenerations. Each have added stress on the oils we use, not to mention the closer tolerances and, in some cases, more exotic metals and materials used. On my 2011 I had two oil analysis done, the first at 3500 miles (it came back showing good results other than for silicone as I recall.) Dealer changed out the oil as the one free one and I then ran the Ford 10/30 Diesel oil until the message came up to change it (at about 6K (9K odometer) on the oil as I recall). Sent it our for analysis and it came back with TBN fair but there was something about shear that I recall (the viscosity of the oil was compromised.) Bottom line is that the oil no longer had some of its main protection properties remaining. There was also almost 8 percent diesel dilution.

So, long story short - I don't see how we can run extended change intervals on these trucks. Too much stuff going into the oil (diesel, soot, and hopefully not much else) as well as the viscosity reduction over time (shear).
 

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I have never done synthetic before, except in that Fiesta.
A few thoughts...

Synthetics do three things that conventionals do not **easily** handle:

1. Flow better at extremely cold temperatures thereby lubricating parts faster than a conventional can--e.g. a 5W-40 flows faster than a 15W-40.
2. Provide high temperature protection because they do not break down as fast as conventionals.
3. Allow for extended oil changes because the additive package is usually better--e.g. the Total Base Number (TBN) is higher from the start versus a conventional.

However, without a bypass system, I would question if a PSD can do extended OCIs because synthetics cannot help with fuel dilution--only changing the oil will help with that. So that leaves you with #1 and #2 and if those are criteria that you meet, then a synthetic may be for you. I spent some time considering which I would use in my PSD when I first bought it and thus far I have not used a conventional. I have used 3 synthetics and 2 synthetic blends. Plenty of people use conventionals in these trucks and have no problems and put plenty of miles on them. I adopted the severe duty maintenance schedule on my PSD due to the use of biodiesel fuel blends (no plain diesel near me in the Houston area) and more often than not I am operating at sustained ambient temperatures above 100°F (38°C)--at least during the summer.

Now, with all of that said, the cost between conventionals, synblends, and synthetics continues to close (as do the attributes). Note I am not going into the Group II, II+, III, and III+ versus Group IV and V argument when discussing synthetics--I am talking about off the shelf "synthetics". So many times we are not talking about large amounts of money to run a synblend or a synthetic versus a conventional. So "sleep easy at night by using a synthetic" can be found fairly cost effectively for those that want or need it.
 

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Sent it our for analysis and it came back with TBN fair but there was something about shear that I recall (the viscosity of the oil was compromised.) Bottom line is that the oil no longer had some of its main protection properties remaining. There was also almost 8 percent diesel dilution.
If I had to guess, I would say the fuel dilution impacted the viscosity more so than mechanical shearing forces (8% is quite a bit). I also agree with you, in stock form extended OCIs do not seem plausible on these trucks and if one is going to extend, then UOAs better be used to ensure it is done safely.
 

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7500 is about what I get on mine. I changed mine early only when I let it sit a while, which I do a bit more now. Otherwise, I use the oil life monitor without issues.
 
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