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For many years i have put 5-30 oil in my fiat ducato motorhome , this year i was advised to put in 5-40 as it goes abroad, while checking the spec of the offered oil i noticed it was also ll04 so made a mental note of this and did the oil change.
Imagine my shock to find that my mpg dropped immediately by 5 mpg from a healthy 33 mpg to a maximum of 28 now.
the motorhome is taxed to 3850 kg so no lightweight like a zed, but it must affect it. Before you ask nothing has been changed in any way it also made no discernible difference whether the ac was on or off.
I cannot imagine that this oil was in any way different to another 5-40 to affect such a huge swing. This of course is immensely annoying to me and my wallet as in a couple of weeks it will be doing couple of thousand miles. I considered doing another oil change back to 5-30 but this would cost roughly the same as doing nothing and taking the fuel hit, and besides I'm curious to see if anything changes on the continent in warmer weather.

I’m sure you know this already but the W in the oil description, in your case 5w30, means winter. This is all to do with the viscosity of the oil. So the idea is to reduce the viscosity of the oil in low temperatures and increase it in high temperatures. 5w30 is used in temperature from -25°C to 25°C and 5w40 from -25°C to 35°C.
With this in mind it may or may not explain your predicament. Did you get this mpg running the camper at optimal temperature?

33 down to 28 is a big difference. Are you sure there are not other factors at work here.

Did you put on some weight?
Come on now, tell the truth

Chris_D wrote: ↑Wed Aug 14, 2019 7:53 pm Did you put on some weight?
Come on now, tell the truth

wot - in a day ??

Maybe you've got a stowaway or two on board?

buzyg wrote: ↑Wed Aug 14, 2019 5:19 pm 33 down to 28 is a big difference. Are you sure there are not other factors at work here.

yes im sure otherwise i would not have mentioned it

Was it running at top temperature???

You know the rules by now

Keith96 wrote: ↑Wed Aug 14, 2019 10:45 am I’m sure you know this already but the W in the oil description, in your case 5w30, means winter. This is all to do with the viscosity of the oil. So the idea is to reduce the viscosity of the oil in low temperatures and increase it in high temperatures. 5w30 is used in temperature from -25°C to 25°C and 5w40 from -25°C to 35°C.
With this in mind it may or may not explain your predicament. Did you get this mpg running the camper at optimal temperature?

based on your figures you cant run 5-30 in the uk - presumably you park up your car when the sun comes out

firebobby wrote: ↑Wed Aug 14, 2019 10:18 pm
You know the rules by now

what- you want a pic of my van ?

road warrior wrote: ↑Wed Aug 14, 2019 10:20 pm

Keith96 wrote: ↑Wed Aug 14, 2019 10:45 am I’m sure you know this already but the W in the oil description, in your case 5w30, means winter. This is all to do with the viscosity of the oil. So the idea is to reduce the viscosity of the oil in low temperatures and increase it in high temperatures. 5w30 is used in temperature from -25°C to 25°C and 5w40 from -25°C to 35°C.
With this in mind it may or may not explain your predicament. Did you get this mpg running the camper at optimal temperature?

based on your figures you cant run 5-30 in the uk - presumably you park up your car when the sun comes out

http://www.differencebetween.net/object ... -and-5w40/
Here is a bit of reading for you. Maybe when you are asking for advice it would be good manners not to jump all over the people willing to take the time to assist.

Did you leave the handbrake on ?

The key bit from the link is
"Both oils are 5 grade when cold, but 5w30 is 30 grade, and 5w40 40 grade at operating temperatures. 5w40 with higher temperatures in summer has a higher viscosity than 5w30, which contributes to uninterrupted functioning of the motor".
So when the engine is cold, on a cold winter morning, both oils are pretty much the same from a viscosity viewpoint. When your engine is hot (whatever the outside temperature, the cooling system is thermostatically controlled to hit and maintain an optimal temperature) the 30 oil is thinner than the 40. Good if you want to save fuel, bad if you want to protect an older engine.

Keith96 wrote: ↑Wed Aug 14, 2019 10:41 pm

road warrior wrote: ↑Wed Aug 14, 2019 10:20 pm

Keith96 wrote: ↑Wed Aug 14, 2019 10:45 am I’m sure you know this already but the W in the oil description, in your case 5w30, means winter. This is all to do with the viscosity of the oil. So the idea is to reduce the viscosity of the oil in low temperatures and increase it in high temperatures. 5w30 is used in temperature from -25°C to 25°C and 5w40 from -25°C to 35°C.
With this in mind it may or may not explain your predicament. Did you get this mpg running the camper at optimal temperature?

based on your figures you cant run 5-30 in the uk - presumably you park up your car when the sun comes out

http://www.differencebetween.net/object ... -and-5w40/
Here is a bit of reading for you. Maybe when you are asking for advice it would be good manners not to jump all over the people willing to take the time to assist.

Oh don't be so po faced, it was a lighthearted comment, moreover I'm not asking for advise. This post is more an observation shared. Try not to look for insults where none exist. Lighten up will ya? I mean thanks for posting but let's not get too serious here.